8 chemistry questions help

can u please explain these STEP BY STEP
thanks:)

1) what is the mass in grams of 1 mole of P2O5 ?
a. 293.03 g b. 61.96 g c. 46.98 g d. 141.96 g

2) what is the percentage by mass of hydrogen in ordinary water (H2O) ?
a. 60% b. 11% c. 40% d. 20%

3) which of the following has the lowest number of atoms ?
a. Na2P2O3 b. (NH4)3PO4 c. (NH4)2Cr2O7 d. K4Fe(CNO)6

4) a sample of calcium that contains avogadro's number of atoms has a mass of
a. 40g b. 20g c. 160g d. 80g

5) what is the mass of 0.05 moles aluminum sulfate
a. 19.8g b. 17.1g c. 6.15g d. 10.95g

6) the number of atoms in 2.4g of magnesium metal is
a. 3.7 X 10^22 b. 1.7 X 10^22 c. 6.0 X 10^22 d. 2.5 X 10^22

7) what is the empirical formula of C8H603
a. CHO b. C4H3O2 c. C4H3O1 d. C8H6O3

8) a certain coumpound has the following composition: C=40.0% and H=6.7 %. the emperical formula is
a. CHO b. CH2O c. CH d. C6H6O

1) what is the mass in grams of 1 mole of P2O5 ?

1 mol of P2O5 have 2 mol of P and 5 mol of O so
Mass of 1 mol of P2O5 =Mass of{ 2 mol of P+ 5 mol of O}
={(2molx31g mol-1)+(5molx16gmol-1)}=141.96 g
where 1 mol of O =16g and 1 mol of P=31g

2 what is the percentage by mass of hydrogen in ordinary water (H2O)
Mass of 1 mol of H2O={(2molx1gmol-1)+(1mol x16gmol-1)}=18 g
1 mol of H2O have 2 mol of H
So percentage by mass of hydrogen in ordinary water=
(2/18)x100%=11%

3) which of the following has the lowest number of atoms

1 molecule of Na2P2O3 have 2Na , 2P and 3O atoms=7 atoms
1 molecule of (NH4)3PO4 have 3N ,12H,1P and 3O atoms=19 atoms
1 molecule of (NH4)2Cr2O7have 2N,8H ,2Cr and 7O atoms=19 atoms
1 molecule of K4Fe(CNO)6 have 4K , 1Fe, 6C, 6N and 6O atoms=23 atoms

Na2P2O3 has the lowest number of atoms


4) a sample of calcium that contains avogadro's number of atoms has a mass of