Question

how many molecules are in 2.1 moles of hbr?
\frac{6.02\times10^{23}\text{ molecules of hbr}}{1\text{ mol hbr}}=\frac{x}{2.1\text{ mol hbr}}
x = ?\times10^{?}\text{ molecules of hbr}
enter the coefficient in the green - box and the exponent in the yellow box

Explanation:

Step1: Cross - multiply the proportion

We have the proportion $\frac{6.02\times 10^{23}\text{ molecules of HBr}}{1\text{ mol HBr}}=\frac{x}{2.1\text{ mol HBr}}$. Cross - multiplying gives $x=(6.02\times 10^{23})\times2.1$.

Step2: Perform the multiplication

$(6.02\times 10^{23})\times2.1 = 6.02\times2.1\times10^{23}$. Since $6.02\times2.1 = 12.642$, then $x = 12.642\times10^{23}$. In scientific notation, this is $1.2642\times 10^{24}$.

Answer:

$1.2642$, $24$