Question

“$L{{i}_{2}}S{{O}_{4}}$ forms double salts with alum.”
Answer whether the above statement is true or false. If true enter 1, else enter 0.

Answer 1

Recollect what are double salts. Read about the physical properties of lithium and try reasoning the statement.

Complete step by step answer:
- Double salts are salts that contain more than one type of cation or more than one type of anion.
- Double salt is a mixture of two simple salts which crystallize as a single substance having crystalline structure different from both the salts taken individually.
- Alum is a double salt which has hydrated double sulphate salt of aluminium. It is represented as $XAl{{\left( S{{O}_{4}} \right)}_{2}}. 12{{H}_{2}}O$ where X is a monovalent cation such as potassium or ammonium, etc. Generally, alum refers to Potassium alum having the molecular formula, $KAl{{\left( S{{O}_{4}} \right)}_{2}}. 12{{H}_{2}}O$
- Now, let’s have a look at the salt given in the question. In $L{{i}_{2}}S{{O}_{4}}$, lithium is the monovalent cation. To see what monovalent cation means let’s have a look at its electronic configuration.
- Lithium has atomic number 3. Its electronic configuration is $1{{s}^{2}}2{{s}^{1}}$ So, to achieve the nearest noble gas configuration, it tends to easily donate one electron. Lithium is an electropositive element.
- Lithium cation, $L{{i}^{+}}$ has a very small size. It cannot form double salt.
-Therefore, the given statement, “$L{{i}_{2}}S{{O}_{4}}$ forms double salts with alum”, is false.
So, the correct answer is “Option 0”.

Note: Remember lithium is a monovalent cation having a very small ionic radius. Lithium doesn’t form double salts. Double salts are formed by potassium, iron, etc.