Example Problem Stoichiometry 4NH3(g) + 6NO(g)→5N2(g) + 6H2O(g) How many moles of each reactant were there if 13.7 moles of N2(g) is produced? ×4 moles NH3(g) = 10.96 moles NH3(g) ×6 moles NO(g) = 16.44 moles NO(g) So we have 10.96 moles NH3(g) and 16.44 moles NO(g). Problem: What is the mass of 2 moles of H2S ? GFM of H = 1 GFM of S = 32>br> GFM of H2S = 2×1 + 32 = 34 grams / mole ×34 grams = 68 grams Percentage Composition by Mass H2O One mole of water is 18.0152 grams. In that compound, there are two moles of H atoms and 2 x 1.008 = 2.016 grams. That's how many grams of hydrogen are present in one mole of water. There is also one mole of oxygen atoms weighing 16.00 grams in the mole of water. To get the percentage of hydrogen, divide the 2.016 by 18.015 and multiply by 100, giving 11.19%. …show more content…
Empirical Formula and Molecular Formula Caffeine has an elemental analysis of 49.48% carbon, 5.190% hydrogen, 16.47% oxygen, and 28.85% nitrogen. It has a molar mass of 194.19 g/mol. What is the molecular formula of caffeine? 49.48% C, 5.190%H, 16.47% O and 28.85% N Step 1 Assume a mass of 100g so % becomes