A household cleaning agent contains a weak base with the formula NaX. 1.00 g of this compound was dissolved in water to give 100.0 mL of solution. A 20.0 mL sample of the solution was titrated with 0.100 mol L⁻¹ hydrochloric acid, and required 24.4 mL of the acid for neutralisation. What is the molar mass of the weak base?

SSCE HSC Chemistry Concentration and Molarity: A household cleaning agent conta

A household cleaning agent contains a weak base with the formula NaX - HSC - SSCE Chemistry - Question 18 - 2011 - Paper 1

Question 18

A household cleaning agent contains a weak base with the formula NaX. 1.00 g of this compound was dissolved in water to give 100.0 mL of solution. A 20.0 mL sample o... show full transcript

Worked Solution & Example Answer:A household cleaning agent contains a weak base with the formula NaX - HSC - SSCE Chemistry - Question 18 - 2011 - Paper 1

Step 1

Calculate the moles of HCl used

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Answer

The moles of HCl can be calculated using the formula:

$\text{Moles of HCl} = \text{Concentration of HCl} \times \text{Volume of HCl (in L)}$

Here, the concentration is 0.100 mol L⁻¹ and the volume is 24.4 mL, which is 0.0244 L. Thus,

$\text{Moles of HCl} = 0.100 \times 0.0244 = 0.00244 \text{ moles}$

Step 2

Determine the number of moles of the weak base

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Answer

In a neutralization reaction, the moles of HCl will equal the moles of the weak base NaX since they react in a 1:1 ratio. Therefore, the moles of NaX are also 0.00244 moles.

Step 3

Calculate the concentration of the weak base solution

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Answer

Since 1.00 g of NaX was dissolved in 100.0 mL of solution, we can find its concentration:

$\text{Concentration of NaX} = \frac{\text{Moles of NaX}}{\text{Volume of solution (in L)}} = \frac{0.00244}{0.1} = 0.0244 \text{ mol L}^{-1}$

Step 4

Calculate the molar mass of the weak base

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Answer

We can find the molar mass (M) using the formula:

$M = \frac{\text{mass (g)}}{\text{moles}}$

Plugging in the values:

$M = \frac{1.00}{0.00244} \approx 409.84 \text{ g/mol}$

Rounding gives approximately 410 g/mol. Therefore, the correct answer is (D) 410 g.

A household cleaning agent contains a weak base with the formula NaX - HSC - SSCE Chemistry - Question 18 - 2011 - Paper 1

Worked Solution & Example Answer:A household cleaning agent contains a weak base with the formula NaX - HSC - SSCE Chemistry - Question 18 - 2011 - Paper 1

Calculate the moles of HCl used

Determine the number of moles of the weak base

Calculate the concentration of the weak base solution

Calculate the molar mass of the weak base

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