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

$x=(6.02\times 10^{23})\times2.1$

Step2: Calculate the product

$x = 12.642\times 10^{23}$

Step3: Convert to scientific notation

$x=1.2642\times 10^{24}$

Answer:

Coefficient in green box: $1.2642$, Exponent in yellow box: $24$