Question

how many total atoms are in 0.800 g of p₂o₅? total atoms:

Explanation:

Step1: Calculate molar mass of $P_2O_5$

The molar mass of $P$ is approximately $30.97\ g/mol$ and of $O$ is approximately $16.00\ g/mol$. For $P_2O_5$, $M=(2\times30.97)+(5\times16.00)=61.94 + 80.00=141.94\ g/mol$.

Step2: Calculate number of moles of $P_2O_5$

Use the formula $n=\frac{m}{M}$, where $m = 0.800\ g$ and $M = 141.94\ g/mol$. So $n=\frac{0.800}{141.94}\ mol\approx0.005636\ mol$.

Step3: Calculate number of molecules of $P_2O_5$

Use Avogadro's number $N_A = 6.022\times10^{23}\ molecules/mol$. The number of $P_2O_5$ molecules $N_{P_2O_5}=n\times N_A=0.005636\times6.022\times10^{23}\ molecules\approx3.394\times10^{21}\ molecules$.

Step4: Calculate total number of atoms

Each $P_2O_5$ molecule has $2 + 5=7$ atoms. So the total number of atoms $N = 7\times N_{P_2O_5}=7\times3.394\times10^{21}\ atoms\approx2.376\times10^{22}\ atoms$.

Answer:

$2.38\times 10^{22}$ (rounded to 3 significant - figures)