Question

If a steam-jacket eudiometer with $23ml$ of oxygen and $4ml$ of hydrogen are mixed over mercury, determine how much and which gas would be left as uncombined after the mixture is sparked?

• A. $21$mL $O_2$
• B. $3.0$mL $H_2$
• C. $24$mL $O_2$
• D. $28$mL $O_2$

Answer 1

Answer: (A)

$21$mL $O_2$

$2H_2+O_2\to 2H_{2}O$
2 moles of hydrogen will react with 1 mole of oxygen.
Volume is directly proportional to the number of moles.
4 ml of hydrogen will react with $\frac{4\times 1}{2}=2$ ml of oxygen.
$23-2=21ml$ of oxygen will be left uncombined.