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Problem :

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    

Problem : 2Al +3Cl2→2AlCl3

When 80 grams of aluminum is reacted with excess chlorine gas, how many formula units of AlCl3 are produced?


×1 mole Al = 2.96 moles Al    

There is a 1:1 ratio between Al and AlCl3, therefore there are 2.96 moles AlCl3.


= 1.78×1025    

Problem : Sb2S3(s) + 3Fe(s)→2Sb(s) +3FeS(s)

If 3.87×1023 particles of Sb2S3(s) are reacted with excess Fe(s), what mass of FeS(s) is produced?


×1 mole Sb2S3(s) = 0.643 moles Sb2S3(s)    
×3 moles FeS(s) = 1.93 moles FeS(s)    
×88 grams = 170 grams    

Problem : CO(g) +2H2(g)→CH3OH(g)

At STP, what volume of H2(g) is needed to react completely with 8.02×1023 molecules of CO(g)?


×1 mole CO(g) = 1.33 moles CO(g)    
×2 moles H2(g) = 2.66 moles H2(g)    
×22.4 L = 59.7 L    

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