Question

1. brass is an alloy of copper (cu) and zinc (zn). if 8.32 g of copper is mixed with 5.2372 × 10⁻² mol of zinc, how many metal atoms in total are present in the brass alloy?

a) 1.10 × 10²³ metal atoms
b) 8.91 × 10⁻²⁴ metal atoms
c) 7.88 × 10²² metal atoms
d) 7.07 × 10²⁴ metal atoms
e) 3.15 × 10²⁴ metal atoms

Explanation:

Step1: Calculate moles of copper

Use the formula $n=\frac{m}{M}$, where $m$ is mass and $M$ is molar - mass. The molar mass of copper ($Cu$) is $M_{Cu}=63.55\ g/mol$. Given $m_{Cu} = 8.32\ g$, then $n_{Cu}=\frac{8.32\ g}{63.55\ g/mol}\approx0.131\ mol$.

Step2: Calculate total moles of metal atoms

The number of moles of zinc is $n_{Zn}=5.2372\times 10^{- 2}\ mol$. The total number of moles of metal atoms in the alloy, $n_{total}=n_{Cu}+n_{Zn}=0.131\ mol + 5.2372\times 10^{-2}\ mol=0.131\ mol+0.052372\ mol = 0.183372\ mol$.

Step3: Calculate total number of metal atoms

Use Avogadro's number $N_A = 6.022\times 10^{23}\ atoms/mol$. The total number of metal atoms $N=n_{total}\times N_A=0.183372\ mol\times6.022\times 10^{23}\ atoms/mol\approx1.10\times 10^{23}\ atoms$.

Answer:

A. $1.10\times 10^{23}$ metal atoms