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

Excess of Kl and dil ${\mathrm{H}}_2{\mathrm{SO}}_4$ were mixed in 50 ml of ${\mathrm{H}}_2{\mathrm{O}}_2$. The ${\mathrm{l}}_2$ liberated requires 20 ml of 0.1 N ${\mathrm{Na}}_2{\mathrm{S}}_2{\mathrm{O}}_3$. The strength of ${\mathrm{H}}_2{\mathrm{O}}_2$ is

1.  0.68 g/liter

2.  0.58 g/liter

3.  48 g/liter

4.  38 g/liter

An ionic compound is dissolved simultaneously in heavy water and ordinary water. Its solubility is

1. Larger in heavy water

2. Smaller in heavy water

3. Solubility is the same in both heavy water as well as ordinary water.

4. Smaller in water

Hydrogen resembles halogens in many respects for which several factors are responsible. Of the following factors which one is most important in this respect?

1.  Its tendency to lose an electron to form a cation.

2.  Its tendency to gain a single electron in its valence shell to attain stable electronic       configuration.

3.  Its low negative electron gain enthalpy value.

4.  Its small size.

Why does H⁺ ion always get associated with other atoms or molecules?

Metal hydrides are ionic, covalent or molecular in nature. Among LiH, NaH, KH, RbH, CsH, the correct order of increasing ionic character is

1.  LiH > NaH > CsH > KH>RbH

2.  LiH < NaH < KH < RbH < CsH

3.  RbH > CsH > NaH > KH > LiH

4.  NaH > CsH > RbH > LiH > KH

Which of the following hydrides is electron-precise hydride?

1.  ${\mathrm{B}}_2{\mathrm{H}}_6$

2.  ${\mathrm{NH}}_3$

3.  ${\mathrm{H}}_2\mathrm{O}$

4.  ${\mathrm{CH}}_4$