1. Section 2: Stoichiometric Calculations Chapter 8: Quantities in Chemical Reactions

2. Learning Goals 0 List the sequence of steps used in solving stoichiometric problems. 0 Solve stoichiometric problems.

3. Using Stoichiometry 0 Steps to solve mole-to-mole, mole- to-mass, and mass-to-mass stoichiometric problems: 1. Write a balanced chemical equation for the reaction. 2. Determine where to start your calculations by noting the unit of the given substance.

4. Using Stoichiometry 0 If mass (in grams) of the given substance is the starting unit, you must convert to moles. 0 If amount (in moles) of the given substance is the starting unit, convert moles of the given substance to moles of the unknown.

5. Using Stoichiometry 3. The end point of the calculation depends on the desired unit of the unknown substance. 0 If the answer must be in moles, stop you are finished. 0 If the answer must be in grams, convert moles of unknown to grams of unknown using the molar mass as the conversion factor.

6. Example – Mole to Mole 0 Sodium chloride forms by the reaction between sodium and chlorine. How many moles of NaCl result from the complete reaction of 3.4 mol of Cl 2 ? 1. Write a balanced chemical equation:

7. Example – Mole to Mole 2. Decide which mole ratio to use:

8. Example – Mole to Mole 3. Use the mole ratio to convert the starting number of moles to final number of moles.

9. Example – Mole to Mass 0 Magnesium hydroxide neutralizes stomach acid, HCl, to produce water and magnesium chloride. What mass of HCl can be neutralized by 0.550 moles of Mg(OH) 2 ? 1. Write a balanced chemical equation:

10. Example – Mole to Mass 2. Decide which mole ratio to use:

11. Example – Mole to Mass 3. Use the mole ratio to convert the starting number of moles to final number of moles, then use molar mass.

12. Example – Mass to Mass 0 If 2.72 g of KClO 3 (s) decompose into KCl(s) and O 2 (g), then how many grams of oxygen are produced? 1. Write a balanced chemical equation:

13. Example – Mass to Mass 2. Decide which mole ratio to use:

14. Example – Mass to Mass 3. Find the number of moles of the starting substance using molar mass. Use the mole ratio to convert the starting moles to final number of moles, and then use the second molar mass.