# Question #5715d

Jul 27, 2015

(a). $2 \times {10}^{22}$

(b). $4 \times {10}^{22}$

(c). $2 \times {10}^{22}$

(d). $66 \text{mg}$

#### Explanation:

(a).

$C {u}^{2 +} + 2 e \rightarrow C u$

Mass Cu = 2.12g

So moles Cu = $\frac{2.12}{63.6} = 0.033$

So no. atoms Cu = $0.033 \times 6.02 \times {10}^{23} = 2.0 \times {10}^{22}$

(b).

From the above equation 1 mole $C {u}^{2 +}$ ions require 2 moles of electrons to be discharged.

So no. moles electrons $= 0.033 \times 2 = 0.066$

So no. electrons $= 0.066 \times 6.02 \times {10}^{23} = 4 \times {10}^{22}$

(c).

$2 {H}^{+} + 2 e \rightarrow {H}_{2}$

So you can see a mole of hydrogen gas also requires 2 moles of electrons to be discharged.

so no. molecules ${H}_{2} = 2 \times {10}^{22}$.

(d).

No. moles ${H}_{2}$ = no. moles $C u = 0.033$

${M}_{r} {H}_{2} = 2.0$

So mass ${H}_{2} = 0.033 \times 2 = 0.066 \text{g"=66"mg}$