What volume of nitrogen(IV) oxide gas (\text{NO}_2), measured at s.t.p. in \text{dm}^3, is… — JAMB UTME

What volume of nitrogen(IV) oxide gas ( $\text{NO}_2$ ), measured at s.t.p. in $\text{dm}^3$ , is evolved when $3.2\text{ g}$ of pure copper metal reacts completely with excess concentrated trioxonitrate(V) acid?

(Molar mass of $\text{Cu} = 64\text{ g mol}^{-1}$ ; Molar volume of gas at s.t.p. = $22.4\text{ dm}^3\text{ mol}^{-1}$ )

Cevap: 2.24 dm^3

Cevap

2.24 dm^3 of nitrogen(IV) oxide gas is produced at s.t.p.

When copper reacts with concentrated trioxonitrate(V) acid, the reaction follows the stoichiometry

\text{Cu} + 4\text{HNO}_3 \rightarrow \text{Cu(NO}_3)_2 + 2\text{NO}_2 + 2\text{H}_2\text{O}

. Thus,

1\text{ mole}

of copper metal (

64\text{ g}

) yields

2\text{ moles}

\text{NO}_2

gas (

44.8\text{ dm}^3

at s.t.p.). For

3.2\text{ g}

(

0.05\text{ moles}

) of copper, the volume of

\text{NO}_2

formed is

0.10\text{ moles} \times 22.4\text{ dm}^3\text{ mol}^{-1} = 2.24\text{ dm}^3

Adım Adım Çözüm

Write the balanced equation for the reaction of copper with concentrated trioxonitrate(V) acid

\text{Cu} + 4\text{HNO}_3 \rightarrow \text{Cu(NO}_3)_2 + 2\text{NO}_2 + 2\text{H}_2\text{O}

Concentrated trioxonitrate(V) acid acts as a strong oxidizing agent, converting copper to copper(II) ions and reducing itself to brown nitrogen(IV) oxide gas.

Calculate the moles of copper metal present in 3.2 g

3.2 / 64 = 0.05 mol

Number of moles is mass divided by relative molar mass.

Determine the amount of nitrogen(IV) oxide gas produced in moles

2 * 0.05 = 0.10 mol

The stoichiometric mole ratio between Cu and NO2 is 1:2.

Convert moles of nitrogen(IV) oxide gas into volume at s.t.p.

0.10 * 22.4 = 2.24 dm^3

One mole of any ideal gas occupies 22.4 dm^3 at standard temperature and pressure.

Anahtar Kavram

Stoichiometry of copper redox reaction with concentrated trioxonitrate(V) acid producing nitrogen(IV) oxide gas.

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