Question

1. how many cu atoms are there in 7.55 g cu?

Explanation:

Step1: Find molar mass of Cu

The molar mass of Cu is 63.55 g/mol.

Step2: Calculate moles of Cu

$n=\frac{m}{M}=\frac{7.55\ g}{63.55\ g/mol}\approx0.119\ mol$

Step3: Calculate number of atoms

$N = n\times N_A$, where $N_A = 6.022\times10^{23}\ mol^{-1}$. So $N=0.119\ mol\times6.022\times10^{23}\ mol^{-1}\approx7.16\times 10^{22}$

Answer:

$7.16\times 10^{22}$