Question

question 7 of 30
a balloon contains 7.36 g of oxygen gas (o₂). how many oxygen molecules are in the balloon?
the periodic table
a. 1.38×10²³ molecules
b. 15 molecules
c. 236 molecules
d. 4.43×10²⁴ molecules

Explanation:

Step1: Calculate molar mass of O₂

The molar mass of O is 16 g/mol. For O₂, molar mass $M = 2\times16\ g/mol=32\ g/mol$.

Step2: Calculate number of moles of O₂

Number of moles $n=\frac{m}{M}$, where $m = 7.36\ g$ and $M = 32\ g/mol$. So $n=\frac{7.36\ g}{32\ g/mol}=0.23\ mol$.

Step3: Calculate number of molecules

We know that 1 mole of any substance contains $N_A = 6.022\times 10^{23}$ molecules. So number of molecules of O₂, $N=n\times N_A=0.23\ mol\times6.022\times 10^{23}\ molecules/mol = 1.38\times 10^{23}$ molecules.

Answer:

A. $1.38\times 10^{23}$ molecules