Which of the following will not produce hydrogen gas

1. Reaction between Fe and dil. HCl

2. Reaction between Zn and conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$

3. Reaction between Zn and NaOH

4. Electrolysis of NaCl in Nelson's cell

Temporary hardness is caused due to presence of 

1. ${\mathrm{CaSO}}_4$

2. ${\mathrm{CaCl}}_2$

3. ${\mathrm{CaCO}}_3$

4. $\mathrm{Ca}{\left({\mathrm{HCO}}_3\right)}_2$

Calgon ( a water softener) is : 

1. ${\mathrm{Na}}_2\left[{\mathrm{Na}}_4{\left({\mathrm{PO}}_3\right)}_6\right]$

2. ${\mathrm{Na}}_4{\left[{\mathrm{Na}}_2\left({\mathrm{PO}}_3\right)\right]}_6$

3. ${\mathrm{Na}}_2{\left[{\mathrm{Na}}_4\left({\mathrm{PO}}_4\right)\right]}_6$

4. ${\mathrm{Na}}_4{\left[{\mathrm{Na}}_2\left({\mathrm{PO}}_4\right)\right]}_6$

The hair dyes available in the market generally contain two bottles, one containing the dye and the other hydrogen peroxide. Before applying the dye, the two solutions are mixed. The hydrogen peroxide-

1. Is added to dilute the solution of the dye

2. Oxidised the dye to give the desired colour

3. Reduces the dye to give the desired colour

4. Acidifies the solution of the dye

When zeolite (hydrated sodium aluminium silicate) is treated with hard water, the sodium ions are exchanged with

1. ${\mathrm{H}}^{+}$ ions

2. ${\mathrm{Ca}}^{2+}$ions

3. ${\mathrm{SO}}_4^{2-}$ ions

4. ${\mathrm{OH}}^{-}$ ions 

Which of the following statement is correct ?

1. Hydrogen has same ionisation potential as sodium

2. H has same electronegativity as halogens

3. It will not be liberated at anode

4. H has oxidation state +1, zero and -1 

Which one of the following process will produce hard water

1. Saturation of water with ${\mathrm{CaSO}}_4$

2. Addition of ${\mathrm{Na}}_2{\mathrm{SO}}_4$ to water

3. Saturation of water with ${\mathrm{CaCO}}_3$

4. Saturation of water with ${\mathrm{MgCO}}_3$

Which of the following statements is incorrect?

1. The equilibrium mixture between ortho and para hydrogen contains 100% of para form at absolute zero

2. In the absence of catalysts, para-hydrogen can be kept for weeks at room temperature in a glass vessel

3. Para form of hydrogen has opposite spins of the two atoms, while ortho form has parallel spins of the two atoms in the hydrogen molecule

4. Para hydrogen is more stable than ortho form and the latter always tends to revert to the stable para form at high temperatures

Which of the following statements is/are correct for salt like hydrides?

a. Salt like hydrides is formed only by those elements which have very low electronegativity values and can transfer electrons to the hydrogen atom.

b.  Salt like hydrides are solids with ionic lattices.

c.  In fused state they conduct electricity.

d.  The density of salt like hydrides is greater than that of the metal.

1.  a, b, c

2.  a, b, c, d

3.  a, b

4.  b, c

Half liter each of three samples of ${\mathrm{H}}_2{\mathrm{O}}_2$ labeled as 10 vol, 15 vol, and 20 vol are mixed and then each diluted with further half liter of water. The volume strength of resultant ${\mathrm{H}}_2{\mathrm{O}}_2$ solution is

1.  5.5

2.  6.5

3.  7.5

4.  8.5