1. Thursday March 2 8 pm CH 105 Bring pencil & calculator
Test 2 Study Guide
Thursday March 2
8 pm CH 105
Bring pencil & calculator

2. Top 7 Topics Limiting reactants Ionic compounds in water Moles
Molarity
Energy
Enthalpy
Calorimetry Questions

3. Limiting Reactants Theoretical Yield
% Yield = (Actual/Theoretical) x 100
How much is used, formed, left over

4. Ionic Compounds In water Strong / weak electrolytes Ionic equations
Metathesis reactions
Ion Solubility

5. Moles Be able to interconvert mass to moles and moles to mass
How many atoms in 3 g H2 ?
(1 Mole H2 / 2 g H2) (3 g H2) (2 moles atoms / Mole H2 ) =
3 moles atoms
= 18 x 1023 atoms = 1.8 x 1024 atoms

6. Molarity
Interconverting molarity, moles, volume
Dilution

7. Energy
E = q + w

8. Enthalpy Endo , exo, sign of H
Given heat for a certain mass, calculate reaction H
Given H and mass, calculate heat

9. Top 7 Topics Let’s do some examples!
Limiting reactants
Ionic compounds in water
Moles
Molarity
Energy
Enthalpy
Calorimetry

10. Limiting Reactants
Theoretical Yield – how much you expect based upon the amount of reactants.
If one reactant is present in excess, then the other limits how much can be made and is used to determine the theoretical yield.

11. 2H2 + O2  2 H2O If 10 moles of oxygen and 10 moles of hydrogen….
The hydrogen limits the amount of water that can be formed
Based upon 10 moles H2, we can make 10 moles water
Based upon 10 moles O2, we can make 20 moles water.
H2 limits. Theoretical Yield = 10 moles ( 180 g) H2O
At end of reaction, will have 5 moles O2 left over

12. Ionic Compounds In water Strong / weak electrolytes Ionic equations
Metathesis reactions
Ion Solubility

13. Group 1A ( alkali metals) cations soluble
NH4+ soluble
NO3- soluble
CH3CO2- = C2H3O2- = acetate soluble
Will be given a chart for other ions

14. Soluble ionic compounds in water exist as free ions surrounded by water molecules.
Soluble ionic compounds are strong electrolytes
Strong acids or bases (HCl, H2SO4, NaOH) are strong electrolytes
Weak acids or bases (CH3CO2H, acetic acid) are weak electrolytes
Molecules that do not disassociate (CO2, sugar) are non electrolytes.

15. potassium sulfate with barium nitrate
2K+(aq) + SO4-2 (aq) + Ba+2 (aq) + 2 NO3- (aq)  2K+(aq) + 2 NO3- (aq) +BaSO4(s)
SO4-2 (aq) + Ba+2 (aq)  BaSO4(s)

16. Molarity Interconverting molarity, moles, volume
M means moles per liter = moles/L
M = moles/L
If you know two things, can determine the third
If you have moles and volume, can determine molarity
3 moles dissolved in 0.5 L = 3moles/0.5L = 6M

17. (Vconc )(Mconc ) = (Vdil )(Mdil )
Molarity - dilution
(Vconc )(Mconc ) = (Vdil )(Mdil )
If you know 3, can solve for the fourth
How many mL of 3M HCl is needed to make 100mL of 1.5 M HCl?
(Vconc)(3M) = (100mL)(1.5M)
Vconc = 50 mL

18. E = q + w
q > 0 heat transferred from the surroundings to the system (endothermic)
q < 0 heat transferred from the system to the surroundings ( exothermic)
w > 0 work is done by the surroundings on the system
w < 0 work is done by the system on the surroundings
q > 0, w > 0 E > 0
q < 0, w < 0 E< 0

19. Enthalpy
Endothermic H > 0
Exothermic H < 0

20. Given heat for a certain mass, calculate reaction H
If it takes 60 kJ to melt 180 grams of ice, what is H for the following reaction?
H2O(s) H2O(l)
(60kJ / 180g) ( 18 g/mole) = 6 kJ/mole
H = 6kJ

21. Given H and mass, calculate heat
H2O(s) H2O(l) H = 6 kJ
How much heat is needed to melt 900 grams of ice?
(900g)(6 kJ/mole)(1mole/18 g) = 300 kJ

22. Calorimetry Specific Heat = q/(mass x temperature change)
Keep track of units
Mass in grams
Temperature change can be C or K but not F
Don’t confuse J and kJ
Given any 3, be able to calculate the fourth