Question

a penny has a mass of 2.50 g and the moon has a mass of 7.35×10²² kg. use this information to answer the questions below. be sure your answers have the correct number of significant digits.
what is the mass of 1 mole of pennies?
round your answer to 3 significant digits.
how many moles of pennies have a mass equal to the mass of the moon?
round your answer to 3 significant digits.

Explanation:

Step1: Recall Avogadro's number

1 mole of any substance contains $6.022\times 10^{23}$ entities.

Step2: Calculate mass of 1 - mole of pennies

The mass of 1 penny is $m = 2.50\ g$. The mass of 1 mole of pennies $M$ is given by the product of the mass of one penny and Avogadro's number.
$M=2.50\ g\times6.022\times 10^{23}=1.5055\times 10^{24}\ g$. Rounding to 3 significant digits, $M = 1.51\times 10^{24}\ g$.

Step3: Calculate moles of pennies with mass equal to the Moon's mass

The mass of the Moon is $m_{moon}=7.35\times 10^{27}\ kg = 7.35\times 10^{30}\ g$. Let the number of moles of pennies be $n$. We know that $n=\frac{m_{moon}}{M}$.
$n=\frac{7.35\times 10^{30}\ g}{1.51\times 10^{24}\ g}\approx4.87\times 10^{6}$.

Answer:

$1.51\times 10^{24}\ g$
$4.87\times 10^{6}$