Question

Which of the following statements are correct regarding lithium and magnesium? 
I) They react slowly with water 
II) Their bicarbonates are solids 
III) Their chlorides are not soluble in ethanol 
IV) Their nitrates decompose easily on heating 
 

• A. II & III only
• B. I & III only
• C. I & IV only
• D. III & IV only

Hint:

Lithium and magnesium show diagonal relationship in the periodic table, which leads to similar properties like slow reactivity with water and thermal decomposition of nitrates.

Answer 1

The Correct Option is C

Step 1: Analyze reactivity with water.
Lithium and magnesium both react slowly with water, unlike other alkali and alkaline earth metals.
So, Statement I is correct.
Step 2: Nature of bicarbonates.
Lithium bicarbonate does not exist as a solid under normal conditions, and magnesium bicarbonate is only stable in aqueous solution.
So, Statement II is incorrect.
Step 3: Solubility of chlorides in ethanol.
Lithium chloride is soluble in ethanol, and magnesium chloride also shows moderate solubility.
So, Statement III is incorrect.
Step 4: Thermal decomposition of nitrates.
Both lithium and magnesium nitrates decompose on heating to give respective oxides, NO₂, and O₂.
So, Statement IV is correct.
Hence, only Statements I and IV are correct.