How many hydrogen atoms are present in 75.0 g of h2o? 7.53 × 1024 atoms 2.51 × 1024 atoms 4.17 atoms 5.02 × 1024 atoms 75.0 atoms

Your answer would be (D), 5.02 x 10^24 atoms
Mass of H2O is 18.01
75.0 grams = 75.0/18.01 = 4.16 moles
hydrogen atoms = 2(4.16)(6.022 * 1023)

Answer = 5.02 x 1024 atoms

Second solution:
molar mass H2O = 18g/mole
75g H2O = 75/18 = 4.167mole
Molecules in 1 mole = 6.022 x 10^23
Molecules in 4.167 
mole = 4.167(6.022)(10^23) = 2.51(10^24moles)
each H2O molecules contains 2 H Atoms
So, Number of H Atoms = 2.51(10^24)2 
Answer = 5.02 x 10^24

Hope that answers your question

While unproven, it uses facts to support part of a conclusion. it is still factual and has predictive power, however.