STOICHIOMETRY
EXTRA HELP QUESTIONS
These questions are optional, and only for practice.
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1. |
The octane present in gasoline burns according to the following equation: |
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2 C8H18 + 25 O2 ---------------> 16 CO2 + 18 H2O |
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(a) How many moles of O2 are needed to react fully with 4 moles of octane? |
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(b) How many moles of CO2 can form from 1 mole of octane? |
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(c) How many moles of water are produced by the combustion of 6 moles of octane? |
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(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? |
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2. |
Terephthalic acid, an important raw material for making Dacron, a synthetic fibre, is made from para-xylene by the following reaction. |
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C8H10 + 3 O2
------------------> C8H6O4 + 2 H2O
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How much terephthalic acid could be made from 154 grams of para-xylene in moles? In grams? |
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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. |
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2 C + O2 --------> 2 CO |
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In a series of steps, CO acts on Fe2O3, with the overall result |
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Fe2O3 + 3 CO -----------> 2 Fe + 3 CO2 |
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(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? |
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(b) The actual yield of iron in this test was 198 grams. What was the percentage yield? |
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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? |
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5. |
Calculate how many grams of K2Cr2O7 are needed to make 35.8 grams of I2 according to the following equation. |
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K2Cr2O7 + 6 NaI + 7 H2SO4 ------> Cr2(SO4)3 + 3 I2 + 7 H2O + 3 Na2SO4 + K2SO4 |
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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. |
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5 KNO2 + 2 KMnO4 + 3 H2SO4 ------> 5 KNO3 + 2 MnSO4 + K2SO4 + 3 H2O |
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How many moles and how many grams of KMnO4 are needed to carry out this reaction on 11.4 grams of KNO2? |
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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? |
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8. |
Given that XeF6(l) + 3 H2O(l) ---------> XeO3(s) + 6 HF(g) |
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How many moles of: |
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a) water are needed to produce 1 mole of XeO3? |
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b) XeO3 does 59.8 grams represent? |
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c) water are needed to produce 59.8 grams of XeO3? |
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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? |
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Na2CO3(aq) + 2 HCl(aq) ------------> CO2(g) + H2O(l) + 2 NaCl(aq) |
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10. |
Calculate the number of moles of each of the ions in the following solutions. |
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(a) 25.0 mL of 1.30 M KOH |
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(b) 37.5 mL of 0.50 M CaCl2 |
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(c) 20.0 mL of 0.50 M (NH4)2CO3 |
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(d) 35.0 mL of 0.40 M Al2(SO4)3 |
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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? |
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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. |
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(a) What weight of Ca3(PO4)2 will be formed? |
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(b) What will be the concentrations of each of the ions in the mixture after reaction? |
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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? |
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14. |
How many millilitres of 0.600 M HCl solution are needed to supply 4.00 x 10-2 mol HCl? |
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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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