How many hydrogen atoms are in 3.25 g of gypsum, CaSO4⋅2H2O\text{CaSO}_4\cdot2\text{H}_2\text{O}CaSO4⋅2H2O (Mr=172.2M_{\text{r}} = 172.2Mr=172.2)?
1.14×10221.14 \times 10^{22}1.14×1022
2.27×10222.27 \times 10^{22}2.27×1022
4.55×10224.55 \times 10^{22}4.55×1022
6.82×10226.82 \times 10^{22}6.82×1022
