Question

what is the mass of 5.60x10^23 molecules of sf₆? (round your answer to the tenths place to maintain 3 significant figures) ______ grams

Explanation:

Step1: Calculate the number of moles

Use Avogadro's number ($N_A = 6.022\times 10^{23}\text{ molecules/mol}$). The number of moles ($n$) of $SF_6$ is given by $n=\frac{N}{N_A}$, where $N = 5.60\times 10^{23}$ molecules.
$n=\frac{5.60\times 10^{23}\text{ molecules}}{6.022\times 10^{23}\text{ molecules/mol}}\approx0.930\text{ mol}$

Step2: Calculate the molar mass of $SF_6$

The molar mass of $S$ is $M_S = 32.07\text{ g/mol}$ and the molar mass of $F$ is $M_F= 19.00\text{ g/mol}$. For $SF_6$, the molar mass $M$ is $M = 32.07\text{ g/mol}+6\times19.00\text{ g/mol}=32.07\text{ g/mol}+ 114.0\text{ g/mol}=146.07\text{ g/mol}$

Step3: Calculate the mass

Use the formula $m = n\times M$. Substitute $n = 0.930\text{ mol}$ and $M = 146.07\text{ g/mol}$ into the formula.
$m=0.930\text{ mol}\times146.07\text{ g/mol}\approx135.8451\text{ g}$
Rounding to 3 - significant figures and to the tenths place gives $m = 135.8\text{ g}$

Answer:

$135.8$