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STOICHIOMETRY EXTRA HELP QUESTIONS
These questions are optional, and only for practice.
 

1.

The octane present in gasoline burns according to the following equation:

 

2 C8H18 + 25 O2 ---------------> 16 CO2 + 18 H2

 

(a) How many moles of O2 are needed to react fully with 4 moles of octane? 

 

(b) How many moles of CO2 can form from 1 mole of octane?

 

(c) How many moles of water are produced by the combustion of 6 moles of octane? 

 

(d) If this reaction is to be used to synthesize 8 mole of CO2, how many moles of oxygen are needed? How many moles of octane? 

2.

Terephthalic acid, an important raw material for making Dacron, a synthetic fibre, is made from para-xylene by the following reaction.

 

C8H10 + 3 O2 ------------------> C8H6O4 + 2 H2O
para-              special conditions    terephthalic
xylene                                                acid

 

How much terephthalic acid could be made from 154 grams of para-xylene in moles? In grams?

3.

The chief process for converting iron ore, Fe2O3, into iron involves the combined action of coal and oxygen. Partial combustion of the carbon in coal give carbon monoxide.

 

2 C + O2 --------> 2 CO

 

In a series of steps, CO acts on Fe2O3, with the overall result

 

Fe2O3 + 3 CO -----------> 2 Fe + 3 CO2

 

(a) In an experiment done on a very small scale to test the efficiency of new approaches, a sample of 324 grams of Fe2O3 was converted into iron. How much iron, in theory, could form from this sample, in moles? In grams?

 

(b) The actual yield of iron in this test was 198 grams. What was the percentage yield?

4.

Aluminum oxide, Al2O3, a buffing powder, is to be made by combining 5.00 grams of aluminum with oxygen, O2. How much oxygen is needed in moles? In grams?

5.

Calculate how many grams of K2Cr2O7 are needed to make 35.8 grams of I2 according to the following equation.

 

K2Cr2O7 + 6 NaI + 7 H2SO4 ------>  Cr2(SO4)3 + 3 I2 + 7 H2O + 3 Na2SO4 + K2SO4

6.

The nitrite ion (NO2-) in potassium nitrite is changed to the nitrate ion by the action of potassium permanganate (KMnO4) in sulphuric acid solution.

 

5 KNO2 + 2 KMnO4 + 3 H2SO4 ------>  5 KNO3 + 2 MnSO4 + K2SO4 + 3 H2O

 

How many moles and how many grams of KMnO4 are needed to carry out this reaction on 11.4 grams of KNO2?

7.

If 2.56 grams of chlorine, Cl2, are to be used to prepare dichlorine heptoxide, Cl2O7, how many moles and how many grams of oxygen are needed?

8.

Given that XeF6(l) + 3 H2O(l) ---------> XeO3(s) + 6 HF(g)

 

How many moles of:

 

a) water are needed to produce 1 mole of XeO3?

 

b) XeO3 does 59.8 grams represent?

 

c) water are needed to produce 59.8 grams of XeO3?

9.

How many grams of CO2 gas are released when a 50.0 grams sample of Na2CO3 that is 60.0 percent pure reacts completely with excess HCl?

 

Na2CO3(aq) + 2 HCl(aq) ------------> CO2(g) + H2O(l) + 2 NaCl(aq)

10. 

Calculate the number of moles of each of the ions in the following solutions.

 

(a) 25.0 mL of 1.30 M KOH

 

(b) 37.5 mL of 0.50 M CaCl2

 

(c) 20.0 mL of 0.50 M (NH4)2CO3

 

(d) 35.0 mL of 0.40 M Al2(SO4)3

11.

Epsom salts is MgSO4.7H2O. How many grams of this compound are needed to react completely 100.0 mL of 0.100 M BaCl2 solution?

12.

A mixture is prepared by adding 20.0 mL of 0.200 M Na3PO4 to 30.0 mL of 0.150 M Ca(NO3)2.

 

(a) What weight of Ca3(PO4)2 will be formed?

 

(b) What will be the concentrations of each of the ions in the mixture after reaction?

13.

How many millilitres of 0.500 M KOH are needed to react completely with 60.0 mL of 0.250 M FeCl2 solution to precipitate Fe(OH)2?

14.

How many millilitres of 0.600 M HCl solution are needed to supply 4.00 x 10-2 mol HCl?

15.

A solution is labelled 0.230 M Fe2(SO4)3. How many moles of Fe3+ and SO42- are in 75.0 mL of this solution?


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