While preparing `20%` aqueous sodium hydroxide solution in a beaker certain observations are recorded . Which of the following statements are correct ?
I . Sodium hydroxide is in the form of pellets flakes .
II . It dissolves in water readily .
III . The beaker appears cold when touched from outside immediately after adding sodium hydroxide to water .
IV . When red litmus paper is dipped into the solution , it turns blue .

Options

A. I , II and III
B. II , III and IV
C. III , IV and I
D. I , II and IV

Explanation

To determine which statements about the preparation of a 20% aqueous sodium hydroxide solution are correct, let's analyze each statement step by step.

### Step 1: Analyze Statement I
**Statement I:** Sodium hydroxide is in the form of pellets or flakes.

- **Explanation:** Sodium hydroxide (NaOH) is typically available in solid form, often as pellets or flakes. This statement is correct.

### Step 2: Analyze Statement II
**Statement II:** It dissolves in water readily.

- **Explanation:** Sodium hydroxide is highly soluble in water. When added to water, it dissociates completely into sodium ions (Na⁺) and hydroxide ions (OH⁻). This statement is also correct.

### Step 3: Analyze Statement III
**Statement III:** The beaker appears cold when touched from outside immediately after adding sodium hydroxide to water.

- **Explanation:** The dissolution of sodium hydroxide in water is an exothermic reaction, meaning it releases heat. Therefore, the beaker will feel warm or hot to the touch, not cold. This statement is incorrect.

### Step 4: Analyze Statement IV
**Statement IV:** When red litmus paper is dipped into the solution, it turns blue.

- **Explanation:** Sodium hydroxide is a strong base. Bases turn red litmus paper blue. Thus, this statement is correct.

### Conclusion
Based on the analysis:
- Statement I: Correct
- Statement II: Correct
- Statement III: Incorrect
- Statement IV: Correct

### Final Answer
The correct statements are I, II, and IV.