University:
Dakota State University
Course:
CHEM 112 | General Chemistry I
Academic year:

2021
Views:

59

Pages:

2
Author:

Jasmine Esparza

Molar Ratios and Mass Relationships in Chemical Equations Given the reaction: CaCl2 (aq) + Na2C2O4 (aq)  CaC2O4 (s) + NaCl (aq) a) If 0.043g of oxygen was produced, how many grams of chlorine reacted? b) How many moles of CaCl2 reacted? c) How many moles of NaCl were produced if 4.39g of Na2C2O4 reacted? STEP 1: Make sure the equation is balanced! The equation is not balanced. Adding a 2 in front of NaCl in the products yields: CaCl2 (aq) + Na2C2O4 (aq)  CaC2O4 (s) + 2 NaCl (aq) Ca 1 1 Ca Cl 2 2 1 Cl Na 2 2 1 Na C2O4 1 1 C2O4 Now the equation has equal numbers of each atom in both reactants and products. a) If 0.043g of oxygen was produced, how many grams of chlorine reacted? STEP 2: Set up the units going from what we have to what we want. what we have what we want 0.043 g O = gO ? g Cl mole O mole CaC2O4 mole CaCl2 gO mole O mole CaC2O4 mole Cl mole CaCl2 g Cl mole Cl Cancel the units until the desired unit is the only one left. STEP 3: Calculate any molar masses (formula weights) needed and fill in the numbers using the balanced equation to find the molar ratios. 0.043 g O 1 mole O 1 mole CaC2O4 1 mole CaCl2 16.00 g O 4 mole O molar mass molar ratio 2 mole Cl 35.45 g Cl 1 mole CaC2O4 1 mole CaCl2 1 mole Cl molar ratio molar ratio molar mass = 0.048 g Cl b) How many moles of CaCl2 reacted? STEP 2: Set up the units going from what we have to what we want. what we have what we want 0.043 g O = ? mole CaCl 2 gO mole O mole CaC2O4 mole CaCl2 gO mole O mole CaC2O4 Cancel the units until the desired unit is the only one left. STEP 3: Calculate any molar masses (formula weights) needed and fill in the numbers using the balanced equation to find the molar ratios. 0.043 g O 1 mole O 1 mole Ca C2O4 1 mole Ca Cl2 16.00 g O molar mass c) 4 mole O molar ratio = 6.7 x 10-4 mole Cl 1 mole Ca C2O4 molar ratio How many moles of NaCl were produced if 4.39g of Na2C2O4 reacted? STEP 2:Set up the units going from what we have to what we want. what we have what we want 4.39 g Na2C2O4 = ? mole NaCl g Na 2C2O4 mole Na 2C2O4 g Na 2C2O4 mole NaCl mole Na 2C2O4 Cancel the units until the desired unit is the only one left. STEP 3: Calculate any molar masses (formula weights) needed and fill in the numbers using the balanced equation to find the molar ratios. 4.39 g Na2C2O4 1 mole Na 2C2O4 2 mole NaCl 134.0 g Na2C2O4 1 mole Na 2C2O4 molar mass = 0.0655 mole CaCl2 molar ratio The same basic steps work for all three problems. Remember your significant figures!

Molar Ratios and Mass Relationships in Chemical Equations

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