MTY1101 – MIDTERMS
Balancing Equations
1)
____ Na3PO4 + ____ KOH  ____ NaOH + ____ K3PO4
2)
____ MgF2 + ____ Li2CO3  ____ MgCO3 + ____ LiF
3)
____ P4 + ____ O2  ____ P2O3
4)
____ RbNO3 + ____ BeF2  ____ Be(NO3)2 + ____ RbF
5)
____ AgNO3 + ____ Cu  ____ Cu(NO3)2 + ____ Ag
Moles & Weigth
1. How many moles are in 22 grams of argon?
2. How many grams are in 88.1 moles of magnesium?
3. How many grams are in 0.02 moles of beryllium iodide, BeI2?
4. How many moles are in 68 grams of copper (II) hydroxide, Cu(OH)2?
5. How many moles are in 1.2 x 103 grams of ammonia, NH3?
6. How many grams are in 2.3 x 10-4 moles of calcium phosphate, Ca3(PO3)2?
Percentage Yield
Formula:
1. Calculate the percent yield of a reaction that had a theoretical yield of 3.76 g and an actual
yield of 1.45 g.
2. Calculate the theoretical yield of a reaction that produced 4.5 g of a product with a 38%
yield
3. Calculate the percent yield of a reaction that produced 5.78 g NH4, if its theoretical yield
was 6.78 g.
4. Calculate the percent yield of H2 of a reaction that produced 0.050 moles H2 from 4.5 g
HCl and excess Al in the reaction below:
2 Al + 6 HCl  2 AlCl3 + 3 H2
5. The following reaction is performed with 1.56 g of BaCl2, which is the limiting reagent, 1.82g
of AgCl was obtained and isolated. Calculate the percent yield of AgCl.
BaCl2 + 2 AgNO3  2 AgCl + Ba(NO3)2
Limiting Reagent
1. In an experiment, 3.25 g of NH3 are allowed to react with 3.50 g of O2.
NH3 + O2
NO + H2O.
a. Which is the limiting?
b. Grams of NO?
c. Mass of Excess
2. Suppose we have 3 moles of N2 and H2, how much NH3 will form?
N2 (g) + 3H2 (g)  2NH3 (g)
3. Suppose 12 g of carbon is mixed up with 64 g of Oxygen gas
C (s) + O2 (g)  CO2 (g)
Empirical Formula
1. A 170.00 g sample of an unidentified compound contains 29.84 g sodium, 67.49 g chromium, and
72.67 g oxygen. Find the empirical formula.
2. Determine the molecular formula of the compound with an empirical formula of CH and a formula
mass of 78.110 u.
3. Determine the molecular formula of a compound with an empirical formula of NH2 and a formula
mass of 32.06 u.
4. A compound is found to contain 26.56% potassium, 35.41% chromium, and the remainder oxygen.
Find its empirical formula.
ANSWER KEYS
Balancing Equations
1)
1 Na3PO4 + 3 KOH  3 NaOH + 1 K3PO4
2)
1 MgF2 + 1 Li2CO3  1 MgCO3 + 2 LiF
3)
1 P4 + 3 O2  2 P2O3
4)
2 RbNO3 + 1 BeF2  1 Be(NO3)2 + 2 RbF
5)
2 AgNO3 + 1 Cu  1 Cu(NO3)2 + 2 Ag
Moles & Weigth
1. How many moles are in 22 grams of argon? 0.550688 moles = 0.55 moles
2. How many grams are in 88.1 moles of magnesium? 2141.711 grams = 2140 g
3. How many grams are in 0.02 moles of beryllium iodide, BeI2? 5.2562 grams = 5 g
4. How many moles are in 68 grams of copper (II) hydroxide, Cu(OH)2? 0.6969 moles = 0.70
moles
5. How many moles are in 1.2 x 103 grams of ammonia, NH3? 70.5882 moles = 71 moles
6. How many grams are in 2.3 x 10-4 moles of calcium phosphate? 0.06398g = 0.064 g
Percentage Yield
1. 38.6%
2. 12 g
3. 85.3%
4. 81%
5. 84.55%
Limiting Reagent
1. a. O2; b. 2.63 NO; c. 1.76 g NH3
2. 34 g NH3
3. 44 g CO2
Empirical Formula
1. Na2Cr2O7
2. E.F mass: 13.02 u ; M.F: C6H4
3. E.F mass: 16.03 u; M.F: N2H4
4. K2Cr2O7