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**Final Answers are in BOLD**

STOICHIOMETRY

1. 150 grams of potassium chlorate is decomposed

A. Balanced equation =

**2KClO3 --> 2KCl + 3O2**

B. How many moles of potassium chlorate are there? 150g KClO3 x 1 mol / 122.5g KClO3 =

**1.22 mol KClO3**

C. How many moles of potassium chlorate are formed? 1.22 mol KClO3 x 2 KCl / 2KClO3 =

**1.22 mol KCl**

D. How many moles of oxygen are formed? 1.22 mol KClO3 x 3 O2 / 2KClO3 =

**1.83 mol O2**

E. What is the mass of the potassium chloride? 74.5g x 1.22 mol =

**90.89g KCl**

F. What is the mass of the oxygen? 32g x 1.83 mol =

**58.56g O2**

G. What is the volume of the oxygen? 1.83 mol O2 x 22.4L / 1 mol =

**40.992 L O2**

2. Iron (III) reacts with hydrochloric acid. If 25 liters of hydrogen gas are formed at STP.

A. Balanced Equation.

**2Fe3 + 18 HCl --> 6FeCl3 + 9H2**

B. What is the mass of the Iron (III)? 25/22.4 = 1.12 mol H2

1.12 mol H2 x 2 mol Fe3/9 mol H2 = 0.25 mol Fe3

0.25 mol Fe3 x 56g Fe3 =

**14g Fe3**

C. What is the mass of the hydrochloric acid? 1.12 mol H2 x 18 mol HCl/9 mol H2 = 2.24 mol HCl

2.24 mol HCl x 36.5g HCl/1 mol HCl =

**81.76g HCl**

D. What is the mass of the Iron (III) Chloride? 1.12 mol H2 x 6 mol FeCl3/9 mol H2 = 0.75 mol FeCl3

0.75 mol x 91.5g FeCl3/1 mol FeCl3 =

**68.63g FeCl3**

E. What is the mass of the Hydrogen gas? 1.12 mol x 2g H2/1 mol H2 =

**2.24g H2**

3. Phosphorous reacts with Oxygen to yield Diphosphorous Pentaoxide (gas). If 50 liters of Oxygen is used:

A. Balanced Equation.

**4P +5O2 --> 2(P2O5)**

B. What is the volume of the Diphosphorous Pentaoxide? 50 L/22.4L = 2.23 mol O2

2.23 mol O2 x 2 mol P2O5/5 mol O2 = 0.89 mol P2O5

0.89 mol P2O5 x 22.4 L/1 mol P2O5 =

**19.94 L P2O5**

C. What is the mass of the Diphosphorous Pentaoxide? 0.89 mol P2O5 x 142g P2O5/1 mol P2O5 =

**126.38g P2O5**

D. What is the mass of the Phosphorous? 2.23 mol O2 x 4 mol P/5 mol O2 = 1.78 mol P

1.78 mol P x 31g P/1 mol P =

**55.18g P**

E. What is the mass of the Oxygen? 2.23 mol O2 x 32g O2/1 mol O2 =

**71.36g O2**

F. How many molecules of oxygen was used? 2.23 mol O2 x 6.02x10^23 mc O2 =

**13.42x10^23 mc O2**

G. How many molecules of Diphosphorous Pentaoxide were formed? 0.89 mol P2O5 x 6.02x10^23 mc P2O5 =

**5.36x10^23 mc P2O5**

H. How many atoms of Phosphorous reacted? 1.78 mol P x 6.02x10^23 atoms P =

**10.72x10^23 at P**

LIMITING REAGENTS

1. 2.8 moles of H2O reacts with 3.1 moles of Cl2O7

A. Balanced equation.

**Cl2O7 + H2O --> 2HClO4**

B. What is the limiting reagent?

**H2O**

C. How many moles of the product are produced? 2.8 mol H2O x 2 mol HClO4/1 mol H2O =

**5.6 mol HClO4**

D. How many moles of the excess reagent remains unreacted? 3.1 mol Cl2O7 - 2.8 mol H2O =

**0.3 mol Cl2O7**

2. 9.8 moles of Al reacts with 12.4 moles of CuSO4

A. Balanced equation.

**2Al + 3CuSO4 --> 3Cu + Al2(SO4)3**

B. What is the limiting reagent?

**Aluminum**

C. How many moles of Al2(SO4)3 are produced? 9.8 mol Al x 1 mol Al2(SO4)3/2 mol Al =

**4.9 mol Al2(SO4)3**

D. How many moles of the excess reagent remain? 12.4 mol CuSO4 - 9.8 mol Al =

**2.6 mol CuSO4**

3. 2.4 grams of Na reacts with 36 grams of H2O

A. Balanced Equation.

**2Na + H2O --> Na2O + H2**

B. What is the limiting reagent?

**H2O**

C. How many moles of H2 are formed? 36g H2O x 1 mol H2O/18g H2O = 2 mol H2O

2 mol H2O x 1 mol H2/1 mol H2O =

**2 mol H2**

D. How many grams of H2 are formed? 2 mol H2 x 2g H2/1 mol H2 =

**4g H2**

E. How many grams of the excess reagent are left? 2.4g Na - 1.2g =

**1.2g Na**

F. How many liters of H2 are formed? 2 mol H2 x 22.4 L H2/1 mole H2 =

**44.8 L H2**

4. 123g of Fe reacts with 56g of O2

A. Balanced Equation.

**4Fe + 3O2 --> 2Fe2O3**

B. What is the limiting reagent?

**O2**

C. How many grams of Fe2O3 are formed? 56g O2 x 2 mol Fe2O3/3 mol O2 =

**37.3g Fe2O3**

D. How many grams of the excess reagent are left? 123g Fe x 3 mol O2/4 mol Fe = 92.25g Fe

123g Fe - 92.25g Fe =

**30.75g Fe**

All help is greatly appreciated. Thank you.