What volume of nitrogen(IV) oxide gas, measured at standard temperature and pressure (STP)… — JAMB UTME

What volume of nitrogen(IV) oxide gas, measured at standard temperature and pressure (STP), is evolved when $12.7\text{ g}$ of copper completely reacts with excess concentrated trioxonitrate(V) acid according to the equation below?

Cu_{(s)} + 4HNO_{3(aq)} \rightarrow Cu(NO_3)_{2(aq)} + 2NO_{2(g)} + 2H_2O_{(l)}

(Relative atomic mass: $Cu = 63.5$ ; Molar volume of gas at STP = $22.4\text{ dm}^3\text{/mol}$ )

$8.96\text{ dm}^3$ Cevap
B
$9.60\text{ dm}^3$
C
$4.48\text{ dm}^3$
D
$17.92\text{ dm}^3$

Cevap

The volume of nitrogen(IV) oxide gas evolved at STP is

8.96\text{ dm}^3

According to the balanced chemical equation,

1\text{ mol}

of copper reacts with excess concentrated trioxonitrate(V) acid to produce

2\text{ mol}

of nitrogen(IV) oxide gas. Since

12.7\text{ g}

of copper corresponds to

0.2\text{ mol}

, the reaction generates

0.4\text{ mol}

NO_2

. At STP,

0.4\text{ mol}

occupies

0.4 \times 22.4 = 8.96\text{ dm}^3

Adım Adım Çözüm

Calculate the amount of copper in moles

\text{Moles of } Cu = \frac{12.7\text{ g}}{63.5\text{ g/mol}} = 0.2\text{ mol}

Dividing given mass by relative atomic mass yields moles of reactant.

Determine moles of

NO_2

gas produced using stoichiometric coefficients

\text{Moles of } NO_2 = 0.2\text{ mol } Cu \times \left(\frac{2\text{ mol } NO_2}{1\text{ mol } Cu}\right) = 0.4\text{ mol}

The balanced chemical equation shows that

1\text{ mol}

Cu

yields

2\text{ mol}

NO_2

gas.

Calculate the volume of

NO_2

gas evolved at STP

\text{Volume of } NO_2 = 0.4\text{ mol} \times 22.4\text{ dm}^3\text{/mol} = 8.96\text{ dm}^3

One mole of any gas occupies

22.4\text{ dm}^3

at standard temperature and pressure.

Anahtar Kavram

Redox stoichiometric calculation of gas volumes produced by trioxonitrate(V) acid reactions

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