Unit 6B Sports Drink
6.4 Solubility and Precipitation
Reviewing double replacement reactions
 The ____________from two reactions replace each other.
 General format: AX + BY = AY + BX
 Ionic compounds are neutral compounds that are solids. In order to be electrolytes
they must be soluble in water. They dissolve to produce cations and anions.
 A ________________ reaction is when 2 soluble substances are mixed together and they
form an _________________substance. This is called a precipitate.
 Precipitation reactions are double replacement reactions.
 Solubility Rules: see reference tables for solubility rules.
Example:
AgNO3 (aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
You Try: Predict the products and identify the precipitate.
BaCl2 + K2CO3 
6.5 Stoichiometry
 The __________________of the balanced equation tell how many moles of each substance
is used in the reaction.
 Mole ratio:
 Stoichiometry: Using the mole ratio from the ___________ ________________ and
information about one compound in the reaction to determine information about
another compound in the equation
Example: What is the mole ratio of chlorine to sodium in the following reaction?
2Na + Cl2  2NaCl
6.5 a: General Stoichiometry
1 step problem
1. If 4.2 moles of H2 reacts completely with O2, how many moles of O2 are needed?
2 H2 + O2  2 H2O
2. Given the BALANCED EQUATION: 2KNO3  2KNO2 + O2, how many moles of oxygen
are produced by the decomposition of 0.67 moles of potassium nitrate?
Moles and Mass stoichiometry : Multi step Problems
We can’t measure moles in the lab. We can measure grams.
 Molar Mass (grams) = 1 mole of a compound
Mole-Mass (2 step problem)
1. How many grams of AgCl will be precipitated if 0.45 mole AgNO3 is reacted as follows:
2 AgNO3 + CaCl2  2 AgCl + Ca(NO3)2
Mass- Mole (2 step problem)
2. Given the BALANCED EQUATION:
2N2 + 3H2  2NH3
How many moles of ammonia (NH3) are produced from 4.42 g of Hydrogen gas (H2)?
HONORS LEVEL ONLY:
Mass - Mass (3 step problem)
1. How many grams Ba(OH)2 are precipitated from 14.5 g of NaOH in the
following reaction:
NaOH + BaCl2  Ba(OH)2 + 2 NaCl
2. Given the UNBALANCED EQUATION: __ Mg + __HCl → __MgCl2 + __H2
How many grams of hydrochloric acid (HCl) are needed to produce 65.0 g of
magnesium chloride?
6.5 b: Stoichiometry and Gases:
 Standard Temperature and Pressure (STP) – 1 atm (or 101.3 kPa or 760 mmHg))
and 273 K (0°C)
 Molar Volume of a Gas – at STP, 1 mole of any gas = 22.4 liters
1. If you need react 1.5 g of zinc completely, what volume of gas will be produced at
STP?
2 HCl (aq) + Zn (s) ZnCl2 (aq) + H2 (g)
2. Given the BALANCED EQUATION:
C3H8 + 5O2 → 3CO2 + 4H2O
How many moles of water will be produced from the complete combustion of 7.3 L of
oxygen?
Keeping all these MOLE equalities straight!
To Go Between
Particles and Moles
Grams and Moles
Moles and liters of a gas at STP
2 different chemicals in a reaction
Use the Equality
1 mole = 6.02 x 1023 atoms, molecules or FU
1 mole = molar mass (grams)
1 mole =22.4 liters at STP
Coefficient ratio (mole ratio) from balanced
equation
Let’s Practice:
1. Given the UNBALANCED EQUATION: __Zn + __HCl  __ZnCl2 + __H2, how many
moles of hydrogen(H2) are produced from the reaction of 1.54 moles of zinc(Zn)
with an excess of hydrochloric acid?
2. Give the UNBALANCED EQUATION: __S8 + __O2 → __SO3
How many liters of sulfur trioxide(SO3) will be produced when 5.43 L of oxygen(O2)
react with an excess of sulfur, S8?
This problem is an example of Law of Combining Volumes
 When pressure & temperature are constant, the mole ratio is the same as the
volume ratio.
 1 step conversion from liters of 1 substance to liters of another substance
So you could just do this:
3. Given the BALANCED EQUATION: 2NaCl + Pb(NO3)2  PbCl2 + 2NaNO3
How many moles of sodium chloride(NaCl) are needed to completely react with 4.0
grams of lead nitrate(Pb(NO3)2)?
6.5 c: Percent Yield and Titrations




Yield= product
Actual Yield(A): the actual amount of product produced in the lab
Theoretical Yield (T) : the amount of product you should produce if nothing went wrong;
use the balanced chemical equation to calculate
Percent yield: ratio of the actual amount produced compared to the amount predicted
%yield =
𝑨
𝑻
x 100
Let’s Practice:
1. a. If 4.2 moles of H2 reacts completely with O2, how many grams of H2O are produced?
2H2 + O2  2 H2O
b. What is the percent yield if 151 grams of H2O are produced?
2. You have precipitated 8.5 g of Ba(OH)2. If you start with 4.57 grams NaOH, what is the percent
yield?
2 NaOH + BaCl2  Ba(OH)2 + 2 NaCl
Titrations

Use a buret to titrate unknown concentration of solutions


The _______________________is the unknown concentration in the Erlenmeyer flask and the
____________________ is the known concentration in the buret
_________________: Addition of a known volume of a known concentration solution (acid or
base) to a known volume of unknown concentration solution to determine the
concentration.
o Formula:
nM1V1 = nM2V2
n=number of moles
M = molarity
V= volume

__________________ (or Stoichiometric Point) – When there is no reactant left over—they have
all be reacted and the solution contains only products
 __________________: Paper or liquid that change color based on pH level. It is used to show
when the endpoint has been reached
 __________________: point at which the indicator changes color.
Examples
1. How many liters of 0.10 M NaOH is needed to react with 0.125 L of 0.25 M BaCl2?
2 NaOH + BaCl2  Ba(OH)2 + 2 NaCl
2. What is the molarity of a Ca(OH)2 solution if 30.0 ml of the solution is neutralized by 20 ml of a
0.50 M solution of HCl?
3. What is the volume of 2.0M solution of NH4OH is needed to neutralize 50.0 ml of a 0.50
M solution of H2SO4?