Mass to Mass Stoichiometry Honors Chemistry Unit 5

Ex. How many grams of copper (I) sulfide could be produced from 7.90 g copper (I) chloride reacting with an excess of H2S gas? Steps to Solve: 1. Write a balanced equation. Determine what you start with and what you want to know. H 2 S + 2CuCl  Cu 2 S +2HCl

2. Convert grams to moles g CuCl 1mole CuCl = mol CuCl 99.0 g CuCl 99.0 g CuCl 3. Covert moles of what you start with to moles of what you want to know using a mole ratio. You get this ratio from the balanced chemical reaction! mol CuCl 1 mol Cu 2 S = mol Cu 2 S 2 mol CuCl 2 mol CuCl 4. Convert moles of what you want to know to grams mol Cu 2 S g Cu 2 S = 6.35 g Cu 2 S 1 mol Cu 2 S 1 mol Cu 2 S H 2 S + 2CuCl  Cu 2 S +2HCl

This can also be done all together as follows: 7.90 g CuCl 1mole CuCl 1 mole Cu 2 S 159.1g Cu 2 S 99.0 g CuCl 2 moles CuCl 1mole Cu 2 S 99.0 g CuCl 2 moles CuCl 1mole Cu 2 S

2NaOH + H 2 SO 4  2H 2 O + Na 2 SO 4 How many grams of sodium sulfate will form if you start with 200. grams of sodium hydroxide and you have an excess of sulfuric acid? 200 g NaOH 1 mole NaOH 40.0 g NaOH 1 mole Na 2 SO 4 2 moles NaOH g Na 2 SO 4 1 mole Na 2 SO 4 = grams Na 2 SO 4

Pb(SO 4 ) 2 + 4LiNO 3  Pb(NO 3 ) 4 + 2Li 2 SO 4 How many grams of lithium nitrate will be needed to make 250. grams of lithium sulfate, assuming you have enough lead (IV) sulfate to complete the reaction? 250.g Li 2 SO 4 1 mole Li 2 SO g Li 2 SO 4 4 moles LiNO 3 2 moles Li 2 SO g LiNO 3 1 mole LiNO 3 = grams LiNO 3

Other Examples 2KClO 3  2KCl + 3O 2 Given moles of KClO 3, how many grams of KCl will form? moles KClO 3 2 moles KClO 3 2 moles KCl g KCl 1 mole KCl grams KCl will form

2PbS+ 3O 2  2PbO + 2SO 2 Given 6.64 x grams of oxygen, how many moles of SO 2 will form? 6.64 x g O 2 1 mole O g O 2 2 moles SO 2 3 moles O 2 = 1.38 x moles SO 2