Question

1. How many atoms are there in 1.7 mol Ca?

Answer 1

answer: 3g. 17kg+3 ÷ 0.25

Answer 2

There are $2.55\times10^{23}$ atoms in 1.7 mol Ca

Solution:

Initially we have to convert the given mass of calcium to moles of calcium, using its molar mass (referring to a periodic table, this is 40.08  g/mol

$1.7 \text { g Ca }\left(\frac{1 \text{ mol Ca}}{40.08 \text{ g Ca}}\right)= 0.0424 \text{ mol Ca}$

Using Avogadro's number, $6.022 \times 10^{23} \text{ particles per mol}$ as $1 \text{ mole }=6.022\times 10^{23}$

We can calculate the number of atoms present by $0.0424 \text{ mol Ca}\times\frac{6.022 \times 10^{23}}{1 \text{ mol }}=2.55\times10^{23} \text { atoms Ca }$