Question

solve a problem involving changing volume and moles of gas.

a balloon containing helium gas expands from \\(230\text{ ml}\\) to \\(860\text{ ml}\\) as more helium is added. what was the initial quantity of helium present if the expanded balloon contains \\(3.8 \times 10^{-4}\text{ mol}\\), assuming constant temperature and pressure?

use the formula: \\(\frac{v_1}{n_1} = \frac{v_2}{n_2}\\)

• \\(1.0 \times 10^{-3}\text{ mol}\\)
• \\(1.4 \times 10^{-3}\text{ mol}\\)
• \\(1.5 \times 10^{-4}\text{ mol}\\)
• \\(1.0 \times 10^{-4}\text{ mol}\\)

Explanation:

Identify the given values and formula

$$
LATEXBLOCK0
$$

Solve for the initial quantity of moles

$$
LATEXBLOCK1
$$

Match with the closest option

$$ n_1 \approx 1.0 \times 10^{-4}\text{ mol} $$

Answer:

• (A) \(1.0 \times 10^{-3}\text{ mol}\)
• (B) \(1.4 \times 10^{-3}\text{ mol}\)
• (C) \(1.5 \times 10^{-4}\text{ mol}\)
• (D) \(1.0 \times 10^{-4}\text{ mol}\) (Correct answer)