Example of how to solve a mass-to-mass stoichiometry problem Example Problem: If 1.00 gram of the simple sugar fructose (C 6 H 12 O 6 ) is burned in atmospheric oxygen of (O 2 ), what mass of carbon dioxide (CO 2 ) would be produced according to the equation below? C 6 H 12 O 6 (s) + 6O 2 (g) 6CO 2 (g) + 6H 2 O(l) Step 1: Interpret the problem and determine what the starting species is. Put the starting species amount, measurement unit, and species formula in a fraction over 1. 1.00 g C H O 1 Your mass-to-mass stoichiometry worksheet Your problem #1: If 2.25 grams of carbon disulfide (CS 2 ) is reacted with an excess amount of fluorine gas (F 2 ), what mass of sulfur (S 8 ) would be produced according to the equation below? 4CS 2 (s) + 4F 2 (g) 4CF 2 (s) + S 8 (s) Step 2: Calculate the molar mass of the starting species in the manner required in this class. The molar mass calculation MUST include an equality statement at the end. C: 12.0107 6 = 72.0642 H: 1.00794 12 = 12.09528 O: 15.9994 6 = 95.9964 180.15588 g C 6 H 12 O 6 = 1 mol C 6 H 12 O 6 180.1559 g C 6 H 12 O 6 = 1 mol C 6 H 12 O 6 Step 3: Use the equality statement from step 2 to write a conversion unit. Put the side of the equality statement that matches the units and species of the starting amount on the bottom. Cancel units and species. Multiply/divide/round. 1.00 g C H O 1 mol C H O 1 180.1559 g C H O 0.00553232 mol C H O 0.00553 mol C H O.
Example of how to solve a mass-to-mass stoichiometry problem (continued) Step 4: Use the answer from step 3 as the new starting amount; put it over 1. Use the coefficients from the balanced chemical equation to write a molar ratio. The molar amount on the bottom of that ratio MUST match the starting amount. The molar amount of the species being sought must be on the top. Cancel units and species. Multiply/divide/round. 0.00553 mol C H O 6 mol CO 2 1 1 mol C H O 0.03318 mol CO 0.0332 mol CO. 2 2 Your mass-to-mass stoichiometry worksheet (continued) Step 5: Use the answer from step 4 as the new starting amount; put it over 1. Calculate the molar mass of the starting species in the manner required in this class. Use the equality statement from the molar mass calculation to write a conversion unit. Cancel units and species. Multiply/divide/round. 0.0332 mol CO2 44.0095 g CO 2 1 1 mol CO2 1.4611154 g CO 1.46 g CO. 2 2 C: 12.0107 1 = 12.0107 O: 15.9994 2 = 31.9988 44.0095 g CO 2 = 1 mol CO 2
Conversion Worksheet 01 Moles of one species to moles of another species conversions Step 1: Starting amount goes over 1. Units of measurement and species must be included. Multiplication sign follows that. Step 2: No equality is needed but a balanced equation is required. Step 3: Build a molar ratio from the coefficients and species in the balanced equation. The coefficients in front of each species in the equation are treated as moles of that species in the molar ratio. The side of the equality statement with units and species that match the starting amount goes on the bottom of the conversion unit. The other side of the equality statement goes on the top of the conversion unit. Step 4: Cancel units and species and solve the problem. Round the answer if needed. Moles of species 1 to moles of species 2 conversion problems: 1. Using the following balanced chemical equation, how many moles of water (H 2 O) will be produced from 4.00 moles of butane (C 4 H 10 ) and an excess of atmospheric oxygen (O 2 )? 2C 4 H 10 (l) + 13O 2 (g) 8CO 2 (g) + 10H 2 O(g) 2. Using the following balanced chemical equation, how many moles of hydrogen gas (H 2 ) will be produced from 2.25 moles of hydrochloric acid (HCl) and an excess of magnesium metal (Mg)? Mg(s) + 2HCl(aq) MgCl 2 (aq) + H 2 (g)
Conversion Worksheet 02 Mole to mass and mass to mole conversions Step 1: Starting amount goes over 1. Units of measurement and species must be included. Multiplication sign follows that. Step 2: Calculate the molar mass of the starting species. The molar mass is the sum of all the atomic masses of all the atoms in a formula. An example of the required format for calculating molar mass in this class is shown below. The example is for silver chloride: Ag: 107.8682 1 = 107.8682 Cl: 35. 453 1 = 35. 453 143.3212 143.321 g AgCl = 1 mol AgCl Note the equality statement at the end of the molar mass calculation. Step 3: Build a conversion unit from the equality statement. The side of the equality statement with units and species that match the starting amount goes on the bottom of the conversion unit. The other side of the equality statement goes on the top of the conversion unit. Step 4: Cancel units and species and solve the problem. Round the answer if needed. Mole to mass conversion problems: 3. What is the mass of 9.99 moles of nickel sulfide (NiS)? Mass to mole conversion problems: 4. How many moles of mercury(ii) sulfide (HgS) are there in 2.25 g of mercury(ii) sulfide?
Conversion Worksheet 03 Mole to particle and particle to mole conversions Step 1: Starting amount goes over 1. Units of measurement and species must be included. Multiplication sign follows that. Step 2: Write equality statement based on the fact that 1 mole of any particles (including atoms, molecules, ions, and formulas) equals 6.02 10 23 of those particles. 6.02 10 23 x = 1 mol x. Step 3: Build a conversion unit from the equality statement. The side of the equality statement with units and species that match the starting amount goes on the bottom of the conversion unit. The other side of the equality statement goes on the top of the conversion unit. Step 4: Cancel units and species and solve the problem. Round the answer if needed. Mole to particle conversion problems: 5. How many atoms are there in 15.00 moles of xenon (Xe)? Particle to mole conversion problems: 6. How many moles are there in 1.22 10 25 molecules of hydrogen cyanide (HCN)?