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If 4.0 g of sodium carbonate reacts with 10 g of hydrochloric acid, it results in the formation of 2.5 g of carbon dioxide and 11.5 g of sodium chloride solution. Show that these results are in accordance with the law of conservation of mass.

The copper oxide was prepared by two different methods. In one case, 1.75 g of the metal gave 2.19 g Of oxide. In the second case, 1.14 g of the metal gave 1.43 g of the oxide. Show that the given data illustrate the law of constant proportions.

Calculate the molecular mass of the substances.
(i) Ammonia
(ii) Hydrochloric acid
(iii) Phosphorus molecule
(iv) Hydrogen molecule
(v) Oxygen molecule
(vi) Sulfur dioxide

Find the mass of
(i) 1 mole of nitrogen atoms
(ii) 8 moles of aluminum atoms
(iii) 0.2 mole of oxygen atoms
(iv) 2 moles of water molecules

Find the number of moles of
(i) 48 g of oxygen gas
(ii) 18 g of ${\mathrm{H}}_2\mathrm{O}$ molecules
(iii) 22 g of ${\mathrm{CO}}_2$ gas
(iv) 51 g of ${\mathrm{NH}}_3$ gas

Calculate the number of moles for the following:-
$$\begin{gathered} \left(\mathrm{i}\right) 84 \mathrm{g} \mathrm{of} \mathrm{nitrogen} \mathrm{atoms} \\ \left(\mathrm{ii}\right) 8.066 \mathrm{x} {10}^{23} \mathrm{number} \mathrm{of} \mathrm{N}-\mathrm{atoms} \left[\mathrm{Atomic} \mathrm{mass} \mathrm{of} \mathrm{N} = 14\right] \end{gathered}$$

In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g of water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass.
$\mathrm{Sodium} \mathrm{carbonate} + \mathrm{Ethanoic} \mathrm{acid} \stackrel{}{\to } \mathrm{Sodium} \mathrm{ethanoate} + \mathrm{Carbon} \mathrm{dioxide} + \mathrm{Water}$

Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
 

Which postulate of Dalton's atomic theory is the result of the law of conservation of mass?

Which postulate of Dalton's atomic theory can explain the law of definite proportions?

Define the atomic mass unit.

Why is it not possible to see an atom with naked eyes?

Write down the formulae of
(i) sodium oxide
(ii) aluminum chloride
(iii) sodium sulfide
(iv) magnesium hydroxide

Write down the names of compounds represented by the following formulae.
$\left(\mathrm{i}\right) {\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3$
$\left(\mathrm{ii}\right) {\mathrm{CaCl}}_2$
$\left(\mathrm{iii}\right) {\mathrm{K}}_2{\mathrm{SO}}_4$
$\left(\mathrm{iv}\right) {\mathrm{KNO}}_3$
$\left(\mathrm{v}\right) {\mathrm{CaCO}}_3$

What is meant by the term chemical formula?

How many atoms are present in a 
$$\begin{gathered} \left(\mathrm{i}\right) {\mathrm{H}}_2\mathrm{S} \mathrm{molecules} \\ \left(\mathrm{ii}\right) {\mathrm{PO}}_4^{3-} \mathrm{ion} \end{gathered}$$

Calculate the molecular masses of 
${\mathrm{H}}_2,$${\mathrm{O}}_2,$${\mathrm{Cl}}_2,$${\mathrm{CO}}_2,$${\mathrm{CH}}_4,$${\mathrm{C}}_2{\mathrm{H}}_6,$${\mathrm{C}}_2{\mathrm{H}}_4,$${\mathrm{NH}}_3,$${\mathrm{CH}}_3\mathrm{OH}$

$$\begin{gathered} \mathrm{Calculate} \mathrm{the} \mathrm{formula} \mathrm{unit} \mathrm{masses} \mathrm{of} \mathrm{ZnO}, {\mathrm{Na}}_2\mathrm{O}, {\mathrm{K}}_2{\mathrm{CO}}_3. \\ \left[\mathrm{Given}, \mathrm{atomic} \mathrm{mass} \mathrm{of} \mathrm{Zn} = 65\mathrm{u}, \mathrm{Na} = 23 \mathrm{u}, \mathrm{K} = 39\mathrm{u}, \mathrm{C} = 12\mathrm{u} \mathrm{and} \mathrm{O} = 16\mathrm{u}\right] \end{gathered}$$

If one mole of carbon atoms weighs 12g. What is the mass (in grams) of 1 atom of carbon?

Which has more number of atoms, 100 g of sodium or 100 g of iron? [Given, the atomic mass of Na= 23 u and Fe= 56 u]

A 0.24 g sample of a compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.

When 3.0 g of carbon is burnt in 8.00 g oxygen,
11.00 g of carbon dioxide is produced. What
mass of carbon dioxide will be formed when
3.00 g of carbon is burnt in 50.00 g of oxygen?
Which law of chemical combination will govern
your answer?

What are polyatomic ions? Give examples.

Write the chemical formulae Of the following.
(i) Copper nitrate
(ii) Aluminium chloride
(iii) Calcium carbonate

Give the names of the elements present in the following compounds.
(i) Quicklime
(ii) Hydrogen bromide
(iii) Baking powder
(iv) Potassium sulfate

Calculate the molar mass of the following substance.
$\left(\mathrm{i}\right) \mathrm{Ethyne} , {\mathrm{C}}_2{\mathrm{H}}_2$
$\left(\mathrm{ii}\right) \mathrm{Sulphur} \mathrm{molecules}, {\mathrm{S}}_8$
$\left(\mathrm{iii}\right) \mathrm{Phosphorus} \mathrm{molecules}, {\mathrm{P}}_4$
$\left(\mathrm{Atomis} \mathrm{mass} \mathrm{of} \mathrm{phosphorus} = 31\right)$
$\left(\mathrm{iv}\right) \mathrm{Hydrochloric} \mathrm{acid}, \mathrm{HCl}$
$\left(\mathrm{v}\right) \mathrm{Nitric} \mathrm{acid}, {\mathrm{HNO}}_3$

what is the mass of
(i) 1 mole of nitrogen atom?
(ii) 4 mole of aluminum atoms
      [Atomic mass of aliminium]
(iii) 10 mole of sodium suphite $\left({\mathrm{Na}}_2{\mathrm{SO}}_3\right)$?

Convert into mole
(i)  12g of oxygen gas
(ii) 20g of water
(iii) 22g of carbon dioxide

What is the mass of
(i) 0.2 mole of oxygen atoms?
(ii) 0.5 mole of water molecules?

Calculate the number of molecules of sulphur ${\mathrm{S}}_8$ present in 16 g of solid sulphur.

Calculate the number of aluminum ions present in 0.051 g of aluminum oxide.
[Hint: The mass of an ion is the same as that of an atom of the same element Atomic mass of Al = 27u]

If 12 g of C is burnt in the presence of 32 g of ${\mathrm{O}}_2$, how much C02 will be formed?
1.  40 g ${\mathrm{CO}}_2$
2.  44 g ${\mathrm{CO}}_2$
3.  30 g ${\mathrm{CO}}_2$
4.  22 g ${\mathrm{CO}}_2$

Which of the following statement is not true about an atom?
1.  Atoms are not able to exist independently
2.  Atoms are the basic units from which molecules and ions are formed
3.  Atoms are always neutral in nature
4.  Atoms aggregate in large numbers to form the matter that we can see, feel or touch

The chemical symbol for sodium is
1.  So
2.  Sd
3.  NA
4.  Na

Which of the following represents 1 amu?
1. Mass of hydrogen molecules
2. $\frac{1}{12}$th of mass of C - 12 atom
3.  Mass of O - 12 atom
4.  Mass of C - 12 atom

Which of the following represents a correct chemical formula?
1.  CaCl
2.  ${\mathrm{BiPO}}_4$
3.  ${\mathrm{NaSO}}_4$
4.  NaS

The formula of chloride of a metal M is ${\mathrm{MCl}}_3$, then the formula of the phosphate of metal M will be 
1.  ${\mathrm{M}}_2{\mathrm{PO}}_4$
2.  ${\mathrm{MPO}}_4$
3.  ${\mathrm{M}}_2{\left(\mathrm{PO}4\right)}_3$
4.  ${\mathrm{M}}_3{\mathrm{PO}}_4$

Calculate the number of aluminum ions which are present in 0.0051 g of aluminum oxides
1.  $6.022 \mathrm{x} {10}^{15} {\mathrm{Al}}^{3+} \mathrm{ions}$
2.  $6.022 \mathrm{x} {10}^{19} {\mathrm{Al}}^{3+} \mathrm{ions}$
3.  $6.022 \mathrm{x} {10}^{14} {\mathrm{Al}}^{3+} \mathrm{ions}$
4.  $6.022 \mathrm{x} {10}^{23} {\mathrm{Al}}^{3+} \mathrm{ions}$

The number of molecules of sulphur $\left({\mathrm{S}}_8\right)$ present in 16 g of solid sulphur will be
1.  $3.76 \mathrm{x} {10}^{16} \mathrm{molecules}$
2.  $3.76 \mathrm{x} {10}^{22} \mathrm{molecules}$
3.  $3.76 \mathrm{x} {10}^{14} \mathrm{molecules}$
4.  $3.76 \mathrm{x} {10}^{26} \mathrm{molecules}$

Which one of the following statements is true?
1.  Mass of 0.5 moles of ${\mathrm{N}}_2$ gas > mass of 0.5 moles of N atoms
2.  Mass of 0.5 moles of ${\mathrm{N}}_2$ gas = mass of 0.5 moles of ${\mathrm{O}}_2$ gas
3.  Mass of 0.5 moles of ${\mathrm{N}}_2$ gas < mass of 0.5 moles of N atoms
4.  Mass of 0.5 moles of ${\mathrm{N}}_2$ gas = mass of 0.5 mole of N atoms

Which statement is correct?
1.  The molar mass of atoms is also known as gram atomic mass
2.  The mass of 1 mole of a substance is equal to its relative atomic or molecular mass in gram
3.  The number of particles present in 1-mole of any substance is fixed, i.e. equal to 6.022 x ${10}^{23}$
4.  All statements are correct

In the following questions, a statement of Assertion (A) is followed by a statement of Reason
Mark the correct choice as :
1.  If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2.  If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
3.  If Assertion is true but Reason is false.
4.  If Assertion is false and Reason is true.
4.  If both Assertion and Reason are false.
 
Assertion Pure water obtained from different sources such as a river, well, spring, sea, etc. always contains hydrogen and oxygen in the ratio of 1: 8 by mass.
Reason A chemical compound always contains elements combined in a fixed proportion by mass.

In the following questions, a statement of Assertion (A) is followed by a statement of Reason
Mark the correct choice as :
1.  If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2.  If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
3.  If Assertion is true but Reason is false.
4.  If Assertion is false and Reason is true.
4.  If both Assertion and Reason are false.
 
Assertion Atomic mass of aluminum is 27.
Reason An atom of aluminum is 27 times heavier than 1/12th of the mass of the carbon-12 atom.

In the following questions, a statement of Assertion (A) is followed by a statement of Reason
Mark the correct choice as :
1.  If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2.  If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
3.  If Assertion is true but Reason is false.
4.  If Assertion is false and Reason is true.
4.  If both Assertion and Reason are false.
 
Assertion Atomic mass has no unit but expressed in amu.
Reason It is the average mass of an atom taking care of the relative abundance of its all isotopes.

In the following questions, a statement of Assertion (A) is followed by a statement of Reason
Mark the correct choice as :
1.  If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2.  If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
3.  If Assertion is true but Reason is false.
4.  If Assertion is false and Reason is true.
4.  If both Assertion and Reason are false.
 
Assertion Molecular weight of ${\mathrm{SO}}_2$ is double to that of ${\mathrm{O}}_2$.
Reason One mole of ${\mathrm{SO}}_2$ contains double the number of molecules present in one mole of ${\mathrm{O}}_2$.

In the following questions, a statement of Assertion (A) is followed by a statement of Reason
Mark the correct choice as :
1.  If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2.  If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
3.  If Assertion is true but Reason is false.
4.  If Assertion is false and Reason is true.
4.  If both Assertion and Reason are false.
 
 
Assertion Magnesium ion and chloride ion combine to form a compound having the chemical formula ${\mathrm{MgCl}}_2$.
Reason Magnesium ion and chloride ion contain + land —2 charges respectively.

How did Berzelius assign symbols to the elements?

Write one example of each.
(a) tetra-atomic molecule
(b) diatomic molecule

Is argon monoatomic or diatomic?

Give the difference between a cation and an anion.

Choose an ionic compound among ${\mathrm{S}}_8, \mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2, {\mathrm{P}}_4, {\mathrm{H}}_2, \mathrm{and} {\mathrm{O}}_2?$

What is the molecular formula of aluminium hydroxide?

What if the chemical formula of ammonium phosphate?

If an element X has its valency equal to 3, what will be its formula with carbonate ion?

Calculate the formula unit mass of ${\mathrm{NaHCO}}_3$.
[Atomic mass of Na u, H = 1 u, C = 12 u, o = 16 u]
 

The molecular mass of water is 18 u. What will be the number of molecules of water in 18 g water?

Calculate the molar mass of sugar $\left({\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\right)$.
[Atomic mass of C = 12u, O = 16u, H = 1u]

How many moles does 24g of Mg contain?

How many moles are present in 4.6g of Na? [Atomic mass of Na = 23u]

(i) State the law of constant proportion.
(ii) In a compound carbon and oxygen react in a ratio 3: 8 by mass to form carbon dioxide. What mass of oxygen is required to react completely with 9 g carbon?

State three points of difference between an atom and molecules.

Calcium carbonate decomposes on heating to form calcium oxide and carbon dioxide. When 10 g of calcium carbonate is decomposed completely then 5.6 g of calcium oxide is formed? Calculate the mass of carbon dioxide formed. Which law of chemical combination will you use in solving this problem? State the law.

Classify each of the following on the basis of their atomicity.
$$\begin{gathered} \left(\mathrm{i}\right) {\mathrm{F}}_2 \left(\mathrm{ii}\right) {\mathrm{NO}}_2 \\ \left(\mathrm{iii}\right) {\mathrm{N}}_2\mathrm{O} \left(\mathrm{iv}\right) {\mathrm{C}}_2{\mathrm{H}}_6 \\ \left(\mathrm{v}\right) {\mathrm{P}}_4 \left(\mathrm{vi}\right) {\mathrm{H}}_2{\mathrm{O}}_2 \\ \left(\mathrm{vii}\right) {\mathrm{P}}_4{\mathrm{O}}_{10} \left(\mathrm{viii}\right) {\mathrm{O}}_3 \\ \left(\mathrm{ix}\right) \mathrm{HCl} \left(\mathrm{x}\right) {\mathrm{CH}}_4 \\ \left(\mathrm{xi}\right) \mathrm{He} \left(\mathrm{xii}\right) \mathrm{Ag} \end{gathered}$$

Give the formulae of the compounds formed from the following sets of elements.
(i)  Calcium and fluorine

(ii)  Hydrogen and sulphur
(iii)  Nitrogen and hydrogen
(iv)  Carbon and chlorine
(v)  Sodium and oxygen
(vi)  Carbon and oxygen

Write the molecular formulae for following compounds.
(i) Copper (II) bromide
(ii) Aluminium (III) nitrate
(iii) Calcium (II) phosphate
(iv) Iron (Ill) sulphide
(v) Mercury (II) chloride
(vi) Magnesium (II) acetate
 

(i) An element X has a valency of 2. Write the chemical formula for
    (a) bromide of the element
    (b) oxide of the element.
(ii) Define the formula unit mass of a substance.

Write the chemical formulae of the following compound, using the criss-cross method.
(i) Magnesium bicarbonate
(ii) Barium nitrate
(iii) Potassium nitrate

Find the ratio by mass of the combining elements in the following compounds.
(i) ${\mathrm{CaCO}}_3$
(ii) ${\mathrm{MgCl}}_2$
(iii) ${\mathrm{H}}_2{\mathrm{SO}}_4$
(iv) ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$
(v) ${\mathrm{NH}}_3$
(vi) $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$

Nitrogen and hydrogen atoms combine in the ratio 14:3 by mass to form ammonia molecules. Find the formula of ammonia molecules by calculating the molar ratio. [Given the atomic mass of N = 14u and H = 1u]

Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one Of them.
(i) Ammonia
(ii) Carbon monoxide
(iii) Hydrogen chloride
(iv) Aluminium fluoride
(v) Magnesium sulphide

$$\begin{gathered} \mathrm{Which} \mathrm{has} \mathrm{more} \mathrm{number} \mathrm{of} \mathrm{atoms}? \\ 100\mathrm{g} \mathrm{of} {\mathrm{N}}_2 \mathrm{or} 100\mathrm{g} \mathrm{of} {\mathrm{NH}}_3 \end{gathered}$$

Calculate the number of aluminum ions present in 2g of aluminum oxide.

Calcium chloride, when dissolved in water, dissociates into its ions according to the following equation,
                        ${\mathrm{CaCl}}_2$(aq) $\stackrel{}{\to }$ ${\mathrm{Ca}}^{2+}$(aq) + $2{\mathrm{Cl}}^{-}$(aq)
Calculate the number of ions obtained from ${\mathrm{CaCl}}_2$ when 222 g of it is dissolved in water.

The mass of a single atom of M is  $3.05 \mathrm{x} {10}^{-22}\mathrm{g}$. What is it's atomic What would this element be?Use periodic table for a possible answer. 

(i) Calculate the number of atoms of hydrogen present in one dozen molecules of hydrogen gas. Convert the given number of hydrogen in terms of number of moles.
(ii) If hydrogen combines with oxygen in the ratio of 1: 8 by mass to form water, how many moles of oxygen would be required for the given amount of hydrogen gas? [Atomic mass of H = 1.0 u and O = 16.0 u]

The mass of, one steel screw is 4.11 g. Find the mass of one mole of these steel screws: Compare this value with the mass of the earth (5.98 x ${10}^{24}$kg). Which one of the two is heavier and by how many times?

Compute the difference in masses of ${10}^3$ moles each of magnesium atoms and magnesium ions. $\left(\mathrm{Mass} \mathrm{of} \mathrm{an} \mathrm{electron} = 9.1 \mathrm{x} {10}^{-31} \mathrm{kg}\right)$

The difference in the mass of 100 moles each of sodium atoms and sodium ions is 5.48002 g. Compute the mass of an electron.

Compute the difference in masses of one mole each of aluminum atoms and one mole each of aluminum atoms and one mole of its ions (Mass of an electron is $9.1 \mathrm{x} {10}^{-28}\mathrm{g}$). Which one is heavier?

A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present in one gram of this sample of gold?

(i) Define Avogadro's number. Write its value.
(ii) Calculate the mass of 0.2 moles of oxygen gas.

Find the mass of each one of the following:
(i) 1 mole of water $\left({\mathrm{H}}_2\mathrm{O}\right)$
(ii) 1 mole of ethanol $\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)$
(iii) 1 mole of glucose $\left({\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\right)$
[Atomic mass of H = 1u, O = 16u, and C = 12u]

Which would weigh more, 2 moles of ${\mathrm{CaCO}}_3$ or 10 moles of ${\mathrm{H}}_2\mathrm{O}$?

Calculate the number of moles present in
 $\left(\mathrm{i}\right) 3.011 \mathrm{x} {10}^{23} \mathrm{number} \mathrm{of} \mathrm{oxygen} \mathrm{atoms}$
$\left(\mathrm{ii}\right) 60\mathrm{g} \mathrm{of} \mathrm{calcium}$
[Given that atomic mass of Ca = 40u, and Avogadro's number = $6.022 x {10}^{23}$]

Calculate the following quantifies in 5.6 g of nitrogen. [Atomic mass of N = 14 u]
(i) Number of moles of ${\mathrm{N}}_2$
(ii) Number of molecules of ${\mathrm{N}}_2$
(iii) Number of atoms of nitrogen
Or A vessel contains 5.6 grams of ${\mathrm{N}}_2$ gas. Calculate the number of moles of ${\mathrm{N}}_2$ gas, the number of nitrogen molecules and the number of nitrogen atoms, if the atomic mass of N = 14.0 u and ${\mathrm{N}}_{\mathrm{A}}$ = $6.022 x {10}^{23}$ per mole.

$\mathrm{Calculate}$
$\left(\mathrm{i}\right) \mathrm{the} \mathrm{mass} \mathrm{of} 1.0505 \mathrm{x} {10}^{23} \mathrm{molecules} \mathrm{of} \mathrm{carbon} \mathrm{dioxide} \left({\mathrm{CO}}_2\right).$
$\left(\mathrm{ii}\right) \mathrm{the} \mathrm{number} \mathrm{of} \mathrm{molecules} \mathrm{in} 0.25 \mathrm{mole} \mathrm{of} {\mathrm{NH}}_3.$
$\left(\mathrm{iii}\right) \mathrm{the} \mathrm{formula} \mathrm{unit} \mathrm{mass} \mathrm{of} {\mathrm{Na}}_2{\mathrm{SO}}_3.$
$[\mathrm{Atomic} \mathrm{mass} \mathrm{of} \mathrm{Na} = 23\mathrm{u}, \mathrm{S} = 32\mathrm{u}, \mathrm{O} = 16\mathrm{u}, \mathrm{H} = 1\mathrm{u}, \mathrm{and} {\mathrm{N}}_{\mathrm{A}} = 6.022 \mathrm{x} {10}^{23} {\mathrm{mol}}^{-1}]$

(i) What is the mass of 0.5 moles of ${\mathrm{NH}}_3$?
    [Given the atomic mass of N = 14 u, the atomic mass of = I u.]
(ii) Calculate the number of particles in 31 g of ${\mathrm{P}}_4$ molecules.
     (Atomic mass of p = 31 u)
(iii) Find the number of moles in 87 g of ${\mathrm{K}}_2{\mathrm{SO}}_4$.
      (Atomic masses of K = 39 u, S = 32 u and 16 u)

Find
(i)   the number of molecules in 90g of ${\mathrm{H}}_2\mathrm{O}$.
(ii)  the number of moles in 19g of ${\mathrm{H}}_2{\mathrm{O}}_2$.
(iii)  formula unit mass of ${\mathrm{Al}}_2{\left({\mathrm{CO}}_3\right)}_3$.
[Atomic mass of Al = 27u, C = 12u, O = 16u, H = 1u, and ${\mathrm{N}}_{\mathrm{A}} = 6.022 \mathrm{x} {10}^{23} {\mathrm{mol}}^{-1}$]

An element ${}_7{}^{14}\mathrm{A}$ exists as diatomic gas in nature which' is relatively inert and forms 78% of earth's atmosphere.
(i) Identify the gas and write its molecular formula. Write the formulae of nitrite and nitrate ions.
(ii) How many moles of this gas would contain 12.044 x atoms of this element? [Avogadro's number=6.022x ${10}^{23}$]
(iii) Calculate the molecular mass of
     (a) ${\mathrm{NH}}_4{\mathrm{NO}}_3$
     (b) ${\mathrm{HNO}}_3$
    [Given atomic masses N = 14u, O = 16u, H = 1u]

Find the number of atoms in 120 g of calcium and 120 g of iron. Which one has more number of atoms and how much is the difference? [Atomic mass of Ca = 40 u, Fe = 56 u]

A sample of ethane $\left({\mathrm{C}}_2{\mathrm{H}}_6\right)$gas has the same mass as $1.5 \mathrm{x} {10}^{20}$molecules of methane $\left({\mathrm{CH}}_4\right)$. How many ${\mathrm{C}}_2{\mathrm{H}}_6$ molecules does the sample of gas contain?

Ravi prepared a solution of sodium chloride by mixing 5.85 g of salt in 1 liter of water. Find
(i) molar mass of sodium chloride.
(ii) the number of moles of sodium chloride dissolved.
     [Atomic masses of sodium and chlorine are 23 u and 35.5 u respectively].
(iii) the concentration of the sodium chloride solution.

Cinnabar (HgS) is a prominent ore of mercury. How many grams of mercury are present in 225 g of pure HgS? The molar mass of Hg and S are 200.6 g ${\mathrm{mol}}^{-1}$ and 32 g ${\mathrm{mol}}^{-1}$ respectively.

If 3.42 g of sucrose is dissolved in 18 g of water in a beaker, then what will be the number of oxygen atoms in the solution?

100 g of a steel block consists of 4.8% carbon and rest is iron. Find the ratio of the number of mole of iron to that of carbon. (Given, the atomic mass of C and Fe = 12 u and 56 u respectively]

How many grams of neutrons are present in a 10g sample of heavy water?

Find the number of copper atom present in 10g of 22-carat gold.
[22-carat gold means 22 out of 24 parts is gold and rest is copper]

In photosynthesis, 6 molecules of carbon dioxide combine with an equal number of water molecules through a complex series of reactions to give a molecule of glucose having a molecular formula ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$. How many grams of water would be required to produce 18 g of glucose? Compute the volume of water so consumed, assuming the density of water to be 1g ${\mathrm{cm}}^{-3}$.

(i) Explain, why the number 01 atoms in one mole of hydrogen gas are double the number of atoms in one mole of helium gas?
(ii) Explain the atomic mass unit
(iii) How many atoms are present in
      (a) ${\mathrm{MnO}}_2$ molecule
      (b) ${\mathrm{CO}}_2$ molecule?

Fill in the blanks.
(i) In a chemical reaction, the sum of the masses of the reactants and products remains unchanged. This is called _______________.
(ii) A group of atoms carrying a fixed
charge on them is called _______________.
(iii) The formula unit mass of is ________________.
(iv) The formulae of sodium carbonate is n. and that of ammonium sulphate is _______________.

Write the molecular formulae of all the compounds that can be formed by the combination of the following ions.
${\mathrm{Cu}}^{2+}, {\mathrm{Na}}^{+}, {\mathrm{Fe}}^{3+}, {\mathrm{Cl}}^{-}, {\mathrm{SO}}_4^{2-}, {\mathrm{PO}}_4^{3-}$

Write the formulae for the following and calculate the molecular mass for each one of them.
(i) Caustic potash   (ii) Baking soda
(iii) Limestone        (iv) Caustic soda
(v) Ethanol             (vi) Common salt

(i) How do we express the number of particles in terms of moles?
(ii) Calculate the number of moles of sodium in a sample containing ${10}^{20}$ atoms of sodium.
(iii) How do we express the mass of a substance in terms of moles?
(iv) Calculate the number of moles in
     (a) 56 g of He 
     (b) 23 g of Na

${\mathrm{SO}}_2$ is an air pollutant released during the burning of fossil fuels and from automobile exhaust'.
(i) Write the names of elements present in this gas.
(ii) What are the valencies of sulphur in ${\mathrm{SO}}_2$ and ${\mathrm{SO}}_3$?
(iii) 'Find, out the number of molecules in 5 moles of ${\mathrm{SO}}_2$.
(iv) Calculate the number of moles in 320 g of ${\mathrm{SO}}_2$ gas.
(v) Calculate the molar mass of 10 moles Of sodium sulphite.
     [Given, atomic masses of S = 32 u, 16 u, Na=23 u and ${\mathrm{N}}_{\mathrm{A}}$=6.022x 1023 per mol]

$\left(\mathrm{i}\right) \mathrm{Calculate} \mathrm{the} \mathrm{number} \mathrm{of} \mathrm{moles} \mathrm{in} 112\mathrm{g} \mathrm{of} \mathrm{iron}.$
$\left(\mathrm{ii}\right) \mathrm{Calculate} \mathrm{the} \mathrm{mass} \mathrm{of} 0.5 \mathrm{mole} \mathrm{of} \mathrm{sugar} \left({\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\right).$
$\left(\mathrm{iii}\right) \mathrm{Define} \mathrm{the} \mathrm{term} \mathrm{molecular} \mathrm{mass}.$
$\left(\mathrm{iv}\right) \mathrm{Determine} \mathrm{the} \mathrm{molecular} \mathrm{mass} \mathrm{of} {\mathrm{AnSO}}_4$
$\left[\mathrm{Atomic} \mathrm{mass} \mathrm{of} \mathrm{Zn} = 65\mathrm{u}, \mathrm{S} = 32\mathrm{u}, \mathrm{and} \mathrm{O} = 16\mathrm{u}\right].$
$\left(\mathrm{v}\right) \mathrm{Calculate} \mathrm{the} \mathrm{number} \mathrm{of} \mathrm{molecules} \mathrm{of} \mathrm{carbon} \mathrm{dioxide}, {\mathrm{CO}}_2 \mathrm{present} \mathrm{in} 4.4\mathrm{g} \mathrm{of} {\mathrm{CO}}_2.$
$\left[\mathrm{Atomic} \mathrm{mass} \mathrm{of} \mathrm{C} = 12\mathrm{u}, \mathrm{O} = 16\mathrm{u}, \mathrm{and} {\mathrm{N}}_{\mathrm{A}} = 6.022 \mathrm{x} {10}^{23} {\mathrm{mol}}^{-1}\right]$

(i) One mole of carbon atoms weighs 12 g. Find the mass of 1 atom of carbon in
[Avogadro's number = $6.022 x {10}^{23}$ per mole]
(ii) Calculate the mass of the following:
     (a) 0.5 mole of ${\mathrm{N}}_2$ gas
     (b) 0.2 mole of O-atoms
     (c) 4 moles of aluminum atom
    [Given, N = 14 u, 16 u, A1 = 27 u, Avogadro's number = $6.022 x {10}^{23}$ per mole]

(i) Which has more number of atoms?
    (a) 10 g of nitrogen $\left({\mathrm{N}}_2\right)$
    (b) 10 g of ammonia $\left({\mathrm{NH}}_3\right)$
(ii) Calculate the total number of moles in 0.585 g of sodium chloride.
[Atomic mass of N = 14u, H = 1u, Cl = 35.5u, Na = 23u]

(i) (a) What mass of silver nitrate will react with 5.85 g of sodium chloride to produce 14.35 g of silver chloride and 8.5 g of sodium nitrate?
     (b) On what law is the above reaction-based and state the law?
(ii) Calculate the number of molecules in 50 g of ${\mathrm{CaCO}}_3$.
(iii) Calculate the mass of 0.5 moles of nitrogen gas.
(iv) Calculate the number of molecules in 50 g of NaCl.
      [Atomic maSs of Ca = 40 u, C = 12 u, O = 16 u, N = 14u, Na = 23u, Cl = 35.5u and ${\mathrm{N}}_{\mathrm{A}} = 6.022\mathrm{x}{10}^{23}$ ${\mathrm{mol}}^{-1}$]

Verify by calculating that
(i) 5 moles of ${\mathrm{CO}}_2$ and 5 moles of ${\mathrm{H}}_2\mathrm{O}$ do not have the same mass.
(ii) 240 g of calcium and 240 g magnesium elements have a mole ratio of 3: 5.

Fill in the missing data in the following table.

A silver ornament of mass m gram is polished with gold equivalent to 1% of the mass of silver. Compute the ratio of the number of atoms of gold and silver in the ornament.

A metal weighing 6 g formed diatomic oxide upon heating in the presence of air. The oxide thus formed weighed 10 g. Write the chemical name of compound.

A sample of pure water, irrespective of its source, contain 11.1% hydrogen and 88.9% oxygen. The data supports
1.  law of multiple proportions
2.  law of reciprocal proportions
3.  law of constant proportions
4.  law of conservation of mass

How many moles are present in 11.5 g of sodium?
1.  0.5 mol
2.  5.0 mob
3.  0.05 mol
4.  1.5 mol

In which of the following, the valency of each of the constituent elements is equal to the total number of atoms in one molecule of the compound?
1. $\mathrm{HCl}$
2.  ${\mathrm{H}}_2\mathrm{S}$
3.  ${\mathrm{MgCl}}_2$
4.  $\mathrm{CaO}$

The chemical symbol for nitrogen gas is
1.  $\mathrm{Ni}$
2.  ${\mathrm{N}}_2$
3.  ${\mathrm{N}}^{+}$
4.  $\mathrm{N}$

What will be the mass of 5 moles of ${\mathrm{SO}}_2$?
1.  310 g
2.  320 g
3.  290 g
4.  120 g

Mark the correct choice as :
1.  If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2.  If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
3.  If Assertion is true but Reason is false.
4.  If both Assertion and Reason are false.
5.  If Assertion is false and Reason is true.
 
Assertion When 10 g of ${\mathrm{CaCO}}_3$ is decomposed, 5.6 g of residue is left and 4.4 g of ${\mathrm{CO}}_2$ escapes.
Reason Law of conservation of mass is followed.

Mark the correct choice as :
1.  If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2.  If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
3.  If Assertion is true but Reason is false.
4.  If both Assertion and Reason are false.
5.  If Assertion is false and Reason is true.
 
Assertion SI unit of atomic mass and molecular mass is kg.
Reason It is equal to the mass of $6.022 x {10}^{23}$ atoms.

Mark the correct choice as :
1.  If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2.  If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
3.  If Assertion is true but Reason is false.
4.  If both Assertion and Reason are false.
5.  If Assertion is false and Reason is true.
 
Assertion Atomicity of ${\mathrm{O}}_3$ is 3.
Reason I mole of an element contains $6.022 \mathrm{x} {10}^{23}$ atoms.

The antacid is prescribed during acidity. Commercially available antacids consist of magnesium hydroxide [$\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$] sugar and flavoring agents. The magnesium hydroxide acts as the base and forms salt and water on reaction with hydrochloric acid of the stomach. The mass of salt and water formed is equal to the combined mass of
1.  $\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$and HCl
2.  $\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$, flavouring agent and HCl
3.  $\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$, sugar and HCl
4.  $\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$, sugar, flavouring agent and HCl

In order to verify the law of conservation of mass, we carry out chemical reactions in a closed container, so that
1.  gaseous products do not escape
2.  heat transfer does not occur
3.  reactants do not mix with the products
4.  None of the above

Which of the following represents a correct chemical formula? Name it.
1.  CaCl
2.  ${\mathrm{BiPO}}_4$
3.  ${\mathrm{NaSO}}_4$ 
4.  NaS

Four students A, B, C, and D verified the law of conservation of mass by performing a chemical reaction between barium chloride and sodium sulphate. All of them took 107.2 g barium chloride solution and 116.1g of sodium sulphate solution and mixed them in the beaker of mass 150 g. They reported their results as follows: Colour of reaction

 
The correct observation is that of student
1.  a
2.  B
3.  C
4.  D

In a chemical reaction, 10.6 g of sodium carbonate reacted with 12 g of ethanoic acid. The products were 4.4 g carbon dioxide, 1.8 g of water and sodium ethanoate. The mass of sodium ethanoate formed is
1.  16.4g
2.  0.16g
3.  24g
4.  8.2g

During experiment hydrogen (${\mathrm{H}}_2$) and oxygen (${\mathrm{O}}_2$) gases reacted in an electric arc to produce water as follows: $2\mathrm{H} + {\mathrm{O}}_2 \stackrel{\mathrm{Electricity}}{\to } 2{\mathrm{H}}_2\mathrm{O}$ 
The experiment is repeated three times and data tabulated as shown below:

During the 3rd experiment, the researcher forgot to list masses of H2 and 02 used. So, if the law of constant proportion is correct then find mass of 02 used during 3rd experiment.

1.  4g
2.   8g
3.  16g
4.  32g

Nitrogen and hydrogen combine together to form ammonia. ${\mathrm{N}}_2 + 3{\mathrm{H}}_2 \stackrel{}{\to } 2{\mathrm{NH}}_3$ [Relative atomic masses of N = 14 u, H= I u]
The mass of nitrogen and hydrogen which combine together to form 6.8 g ammonia is
1.  ${\mathrm{N}}_2$ =2.8g, ${\mathrm{H}}_2$ = 4.0g
2.  ${\mathrm{N}}_2$ = 56g, ${\mathrm{H}}_2$ = 12g
3. ${\mathrm{N}}_2$ = 4.og, ${\mathrm{H}}_2$=2.8g
4. ${\mathrm{N}}_2$ = 12 g, ${\mathrm{H}}_2$ = 5.6g

Which of the following correctly represents 360g of water?
I.  2 moles of 
II.  20 moles of water
III.  $6.022 x {10}^{23}$ molecules of water
IV.  $1.2044 x {10}^{25}$ molecules of water
1.  Only I
2.  I and IV
3.  II and III
4.  II and IV

3.42 g of glucose arc dissolved in 18 g of water in a beaker. The number of oxygen atoms in the solution is
1.  $6.68 \mathrm{x} {10}^{23}$
2.  $6.09 \mathrm{x} {10}^{22}$
3.  $6022 \mathrm{x} {10}^{23}$
4.  $6.022 \mathrm{x} {10}^{21}$

Which of the following contains the maximum number of molecules?
1.  $1\mathrm{g} {\mathrm{CO}}_2$
2.  $1\mathrm{g} {\mathrm{N}}_2$
3.  $1{\mathrm{gH}}_2$
4.  $1{\mathrm{gCH}}_4$