The largest mass fraction of oxygen in the molecule: a) P2O5 b) H2O c) H2SO4 d) Ca (OH) 2

Decision:
1. Let’s find the molecular weight of P2O5:
31 * 2 + 16 * 5 = 142;
2. Let’s find the mass fraction of oxygen in phosphorus oxide:
16 * 5/142 = 80/142 = 0.5634 (56.34%);
3. Find the molecular weight of H2O:
1 * 2 + 16 = 18;
4. Let’s find the mass fraction of oxygen in water:
16/18 = 0.8889 (88.89%);
5. Find the molecular weight of H2SO4:
1 * 2 + 32 + 16 * 4 = 98;
6. Find the mass fraction of oxygen in sulfuric acid:
16 * 4/98 = 64/98 = 0.6531 (65.31%);
7. Find the molecular weight of Ca (OH) 2:
40 + 16 * 2 + 2 = 74;
8. Let’s find the mass fraction of oxygen in calcium hydroxide:
16 * 2/74 = 80/142 = 0.4324 (43.24%);
Answer: the largest mass fraction of oxygen in a water molecule.