16. what is the mass of 9.00x10^19 molecules of cacl₂\n9.00x10^19 / 1 1 mol / 6.02x10^23

Explanation:

Step1: Calculate the number of moles

First, use Avogadro's number ($N_A = 6.022\times 10^{23}$ molecules/mol) to convert the number of molecules to moles. The number of moles $n$ of $CaCl_2$ is given by the formula $n=\frac{N}{N_A}$, where $N = 9.00\times 10^{19}$ molecules. So $n=\frac{9.00\times 10^{19}\text{ molecules}}{6.022\times 10^{23}\text{ molecules/mol}}\approx1.49\times 10^{-4}\text{ mol}$.

Step2: Calculate the molar - mass of $CaCl_2$

The molar - mass of $CaCl_2$: The atomic mass of $Ca$ is approximately $40.08$ g/mol and the atomic mass of $Cl$ is approximately $35.45$ g/mol. Since there are 2 $Cl$ atoms in $CaCl_2$, the molar - mass $M$ of $CaCl_2$ is $M = 40.08\text{ g/mol}+2\times35.45\text{ g/mol}=40.08\text{ g/mol} + 70.90\text{ g/mol}=110.98\text{ g/mol}$.

Step3: Calculate the mass

Use the formula $m = n\times M$, where $n = 1.49\times 10^{-4}\text{ mol}$ and $M = 110.98\text{ g/mol}$. So $m=(1.49\times 10^{-4}\text{ mol})\times(110.98\text{ g/mol})\approx1.65\times 10^{-2}\text{ g}$.

Answer:

$1.65\times 10^{-2}\text{ g}$