AP Chemistry - Chapter 4: Molarity Calculations

AP Chemistry

Chapter 4: Lesson 2

Using Molarity in a Stoichiometry Problem

Chapter 4: Lesson 2 - Using Molarity in a Stoichiometry Problem

Objectives

Be able to calculate the concentration in Molarity of a solution.

Be able to use Molarity in stoichiometric calculations.

Be able to identify number of ions produced in a solution.

Be able to create a solution using the dilution equation.

Vocabulary:

Solute, Solvent, Solution, Dilution, Concentration, Molarity

Introduction to Simple Molarity Calculations

Intro to simple Molarity Calc.mp4

More Simple molarity Practice.mp4

How to Calculate an Excess Reactant and use Molarity

Another aspect of Stoichiometry is using Molarity to make a calculation.

Remember Molarity = mols of solute / Liter of Solution

This can be used as an equality statement inside dimensional analysis.

Watch this video to see how to not only do stoichiometry but to solve for the quantity of unused reactant known as the excess reactant.

stoichiometry with Molarity: excess reactant.mp4

Let's Practice

Check Your Understanding:

For the four questions below, think about the question, then click on the down arrow when you have your answer to check to see if you are correct.

How many grams of Sodium Nitrate are in 30.0mL of 1.55M solution?

30.0mL 1.0L 1.55molesNaNO3 85 grams NaNO3

----------------------------------------------------------------------------------------- = 3.95 grams of NaNO3

1000mL 1.0L 1 mol NaNO3

2. How many Chlorine ions are in 25.0 mL of 0.75M AlCl3 solution?

25.0mL 1.0L 0.75moles 6.02 E 23 3 Cl-

----------------------------------------------------------------------------------------------- = 3.39E22 Remember for every one AlCl3 that goes in solution it will create 3 Cl- ions

1000mL 1 Liter 1 mole 1 AlCl3

How many ions are in Calcium Phosphate?

Ca3(PO4)2 --> 3 Ca + 2 PO4 With 3 Calcium and 2 Phosphates that makes 5 ions.

How many grams of water can be produced by 13.0 mL of 1.2M H2SO4 reacting with excess KOH?

H2SO4 + 2KOH --> 2HOH + K2SO4

13.0mL 1.0L 1.2 moles 18.0grams H20

------------------------------------------------------------------------------ = 0.281 grams H2O

1000 mL 1.0L 1.0moles

Check Your Understanding:

For the three questions below, think about the question, then click on the down arrow when you have your answer to check to see if you are correct.

How would you increase the concentration of a solution?

Add more solute or evaporate out some of the solvent.

2. How would you decrease the concentration of a solution?

Add more solvent usually this means water!

3. Which Diagram best represents Calcium Chloride?

Diagram B- 1 Calcium ion per 2 Chloride ions and they are all separated from each other.

You have finished Lesson 2!

Be sure to head over to google classroom and fill out the exit pass.

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