2 Marks Questions

Question 512 Marks

How would you explain
i. BeO is insoluble but $\mathrm{BeSO}_4$ is soluble in water?
ii. $\mathrm{Be}(\mathrm{OH})_2$ dissolves in NaOH but $\mathrm{Mg}(\mathrm{OH})_2$ does not?

Answer

i. Lattice energy of BeO is greater than its hydration energy so, it is insoluble in water while in case of $\mathrm{BeSO}_4$, hydration energy is greater than lattice energy, so it is readily soluble in water.
ii. $\mathrm{Be}(\mathrm{OH})_2$ is amphoteric and therefore, it dissolves in NaOH forming sodium beryllate
$\mathrm{Be}(\mathrm{OH})_2+2 \mathrm{NaOH} \longrightarrow \mathrm{Na}_2 \mathrm{BeO}_2+2 \mathrm{H}_2 \mathrm{O}$
On the other hand, $\mathrm{Mg}(\mathrm{OH})_2$, is basic and does not dissolve in NaOH .

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Question 522 Marks

What happens when:
i. $\mathrm{LiNO}_3$ is heated.
ii. $\mathrm{KNO}_3$ is heated.
Write the chemical reactions involved.

Answer

i. $4 \mathrm{LiNO}_3 \longrightarrow 2 \mathrm{Li}_2 \mathrm{O}+4 \mathrm{NO}_2+\mathrm{O}_2$
Lithium nitrate, on heating gives $\mathrm{Li}_2 \mathrm{O}, \mathrm{NO}_2$ and $\mathrm{O}_2$ gas.
ii. Potassium nitrate, on heating gives $\mathrm{KNO}_2$ (potassium nitrate) and $\mathrm{O}_2$ gas.
$2 \mathrm{KNO}_3(\mathrm{~s}) \xrightarrow{\text { heat }} 2 \mathrm{KNO}_2(\mathrm{~s})+\mathrm{O}_2(\mathrm{~s})$

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Question 532 Marks

Give one important ore of sodium and potassium element.
What are the raw materials used for the manufacture of washing soda by Solvay process?

Answer

Sodium : NaCl

Potassium : KCl

Raw materials used for the manufacture of washing soda by Solvay process are $\mathrm{NaCl}, \mathrm{CaCO}_3$ and $\mathrm{NH}_3$.

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Question 542 Marks

Why does $\mathrm{BeCl}_2$ react with water to give acidic solution? Give chemical reaction.

Answer

$\mathrm{BeCl}_2$ is covalent, therefore, it gets hydrolysed to form $\mathrm{Be}(\mathrm{OH})_2$ and $\mathrm{HCl}, \mathrm{HCl}$, being strong acid, solution is acidic in nature.
$\text{BeCl}_2+2\text{H}_2\text{O}\xrightarrow{\ \ \ \\ \ \ \ }\text{Be(OH)}_2+2\text{HCl}$

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Question 552 Marks

i. Why is it necessary to remove $\mathrm{CO}_2$ continuously during the manufacture of CaO from $\mathrm{CaCO}_3$ ?
ii. $\mathrm{CaCO}_3 \rightarrow \mathrm{CaO}+\mathrm{CO}_2$ why the temperature of this reaction is maintained at 1270 K ?

Answer

i. As the reaction is reversible in nature, $\mathrm{CO}_2$, formed in the reaction must be removed as soon as it is formed so that the reaction does not proceed in the backward direction.
ii. The temperature shouldn't be allowed to rise above 1270 K , otherwise silica $\left(\mathrm{SiO}_2\right)$ present as impurity in limestone will combine with CaO to form $\mathrm{CasiO}_3$
$\text{CaO}+\text{SiO}_2\xrightarrow{\text{Above } 1270\text{K}}\text{CaSiO}_3$

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Chemistry 2 Marks Questions