In the reaction between sodium hydroxide and tetraoxosulphate (VI) solutions, what volume of 0.5 molar sodium…

1. Analyze the question

We are asked to find the volume of a base (NaOH) required to neutralize a specific volume and concentration of an acid ($H_2SO_4$). This is a classic titration stoichiometry problem.

2. Explain the concept

To solve this, we use the balanced chemical equation for the reaction and the titration formula:

Where:

• $C_a$ = Concentration of the acid
• $V_a$ = Volume of the acid
• $n_a$ = Number of moles of acid from the balanced equation
• $C_b$ = Concentration of the base
• $V_b$ = Volume of the base
• $n_b$ = Number of moles of base from the balanced equation

Balanced Equation: $2NaOH + H_2SO_4 \rightarrow Na_2SO_4 + 2H_2O$ From the equation, $n_a = 1$ and $n_b = 2$.

3. Show the solution

Given:

• $C_a = 1.25\text{ M}$
• $V_a = 10\text{ cm}^3$
• $C_b = 0.5\text{ M}$
• $V_b = ?$
• $n_a = 1$
• $n_b = 2$

Step-by-step calculation: Substitute the values into the formula:

Multiply both sides to clear the fraction:

Now, solve for $V_b$:

4. Identify the answer

The calculated volume is $50\text{ cm}^3$, which corresponds to option D.

5. Tip

Always write out the balanced chemical equation first! Many students forget the stoichiometry coefficients ($n_a$ and $n_b$). If you forget to include the "2" for the NaOH in this reaction, you would get $25\text{ cm}^3$ (Option A), which is a common "distractor" answer designed to catch students who miss the mole ratio.