1.for the reaction p4 o10(s) + 6h2o(l) → 4h3po4(aq), what mass of p
must beconsumed if 5.51 × 10^23 molecules of h2o are also consumed?

can someone me with this?

P₄O₁₀ + 6H₂O → 4H₃PO₄
The equation shows us that the molar ratio of
P₄O₁₀ : 6H₂O = 1:6

We also know that one mole of a substance contains 6.02 x 10²³ particles. We can use this to calculate the moles of water.
moles(H₂O) = (5.51 x 10²³) / (6.02 x 10²³)
= 0.92 mole
That means moles of P₄O₁₀ = 0.92 / 6
= 0.15

Each mole of P₄O₁₀ contains 4 moles of P. 
moles(P) = 4 x 0.15 = 0.6 mol
Mr of P = 207 grams per mol
Mass of P = 207 x 0.6
= 124.2 grams