MOLES, MASS, and VOLUME OF A GAS



MAROOCHYDORE STATE HIGH SCHOOL

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YEAR 11 – CHEMISTRY

SEMESTER ONE

MOLES, MASS, and VOLUME OF A GAS

1. Complete the table below:

|Name |Formula |Molar mass (M) |Moles (n) |Sample mass |

|Sodium Hydroxide |NaOH | | |3.41 g |

| |CCl4 | |1.4 | |

|Sodium Carbonate | |106 amu |1.0 | |

| |KCl | |.25 | |

|Ammonium Phosphate | | | |8.46 g |

2. Find the number of moles in the following samples

a) 14.6 g acetylene, C2H2

b) 0.48 g propane, C3H8

c) 485 g ethanol, C2H5OH

d) 8.5 g Carbon Dioxide, CO2

3. Which of the following substances has the greatest mass?

a) 200 g of Magnesium

b) 5 mol of Sulphur

c) 1.2 x 1024 atoms of helium

4. Sodium Fluoride is thought to reduce tooth decay, especially in children. It is therefore added to some brands of toothpaste. If a tube of toothpaste contains 0.013g of Sodium Fluoride:

a) How many moles of Sodium Fluoride does this represent?

b) How many Sodium ions does this represent?

5. To prevent a gum disease called Scurvy, the minimum daily requirement of Vitamin C (C6H8O6) required is 60 mg.

a) How many moles of Vitamin C is this?

b) How many molecules is this?

c) If 10 g of Spinach is found to contain 1.2 x 10-5 g of Vitamin C, how much Spinach must be eaten each day to get the daily requirement?

6. What would be the volume of:

a) 2.0 moles of Hydrogen gas (H2) at STP

b) 7.5 moles of Oxygen gas at STP

c) 4.0 g of Carbon Dioxide gas at 0oC and 1 atmosphere pressure

d) 30 g of Butane gas (C4H10) at SLC

Questions 7 and 8 deal with the following scenario:

You react chemical A with chemical B to make a single product. It takes 100 g of A to react completely with 20 g of B

7. What is the mass of the product?

a) less than 10 g b) between 100 and 120 g c) exactly 120 g d) over 120 g

8. What is true about the Chemical Properties of the product?

a) the properties are more like chemical A

b) the properties are more like chemical B

c) the properties are an average of those of chemical A and chemical B

d) the properties are not necessarily like either chemical A or B

STOICHIOMETRY

9. Balance the following equations and then determine the number of moles, which reacts or is produced. The first one in (a) has been done for you.

|(a) |______ N2 |+ |_______ Cl2 |( |_______ NCl3 | | |

| | | | | | | | |

| |n (N2) | |n (Cl2) | |n (NCl3) | | |

|(i) |2 | |6 | |4 | | |

|(ii) |4 | |? | |? | | |

|(iii) |3.2 | |? | |? | | |

| | | | | | | | |

|(b) |______ C2H4 |+ |______ O2 |( |______ CO2 |+ |______ H2O |

| | | | | | | | |

| |n (C2H4) | |n (O2) | |n (CO2) | |n (H2O) |

|(i) |? | |.3 | |? | |? |

|(ii) |? | |? | |4 | |? |

|(iii) |6 | |? | |? | |? |

| | | | | | | | |

10. Carbon Dioxide can be prepared in the laboratory by reacting magnesium Carbonate with dilute Hydrochloric acid according to the equation:

MgCO3(s) + 2 HCl(aq) ( MgCl2(aq) + H2O(l) + CO2(g)

If 10.0 g of Hydrochloric Acid is reacted, calculate;

a) the mass of magnesium Carbonate this would react with;

b) the volume of Carbon Dioxide produced at S.T.P.

11. In respiration the equation for the reaction that produces energy in our bodies is

C6H12O6(aq) + 6 O2(g) ( 6 CO2(g) + 6 H2O(l)

If 8.9 g of Glucose is used in this reaction, determine;

a) the mass of Oxygen needed;

b) the volume of carbon Dioxide produced.

12. When sodium is placed on waterit reacts violently to produce hydrogen gas and a solution of aqueous Sodium hydroxide.

a) Write a balanced chemical equation for this process

b) If 3.2 litres of Hydrogen gas is produced by this reaction at SLC what mass of Sodium reacted?

c) What mass of water would completely react with 4.6 g of Sodium?

d) If 1 kilogram of Sodium was placed in 300 mL of water which reactant would be used up first?

13. The reusable booster rockets of the U.S.A. space shuttle employ a mixture of aluminium and Ammonium Perchlorate for fuel. A possible equation for this reaction is;

3 Al (s) + 3 NH4ClO4 (s) ( Al2O3 (s) + AlCl3 (s) + 3 NO (g) + 6 H2O (g)

What mass of NH4ClO4 should be used in the fuel mixture for every kilogram of Aluminium?

14. Elixirs such as Alka-Seltzer use the reaction of Sodium Bicarbonate (NaHCO3) with Citric Acid in aqueous solution to produce a ‘fizz’.

3 NaHCO3 (aq) + C6H8O7 (aq) ( 3 CO2 (g) + 3 H2O (l) + Na3C6H5O7 (aq)

a) What mass of Citric Acid should be used for every 100 mg of NaHCO3 ?

b) What volume of CO2 could be produced from such a mixture at S.T.P.?

PERCENT COMPOSITION

15. Calculate the percent composition of Carbon in Butene, C4H8

16. Calculate the percentage by mass of each element in the following compounds:

a) Al2O3 b) Cu(OH)2

c) MgCl2.6H2O d) Fe2(SO4)3

17. Write the empirical formula for each of the following compounds:

a) Vitamin C, C6H8O6 b) benzene, C6H6 c) Glucose, C6H12O6

18. Many people feel that they cannot do without their morning cup of coffee. Coffee contains the stimulant caffeine. Analysis shows that it consists of 49.48% Carbon, 5.19% hydrogen, 28.85% nitrogen, and 16.48% Oxygen by mass. Calculate the Empirical formula of Caffeine.

19. The amino acid Cysteine contains the elements Carbon, Hydrogen, Nitrogen, Oxygen, and Sulphur. Analysis of a 1.21 g sample of Cysteine shows that it contains; .0704 g of Hydrogen atoms, 1.8 x 1022 Carbon atoms, 0.14 g of Nitrogen atoms, and equal masses of Oxygen and Sulphur atoms. Find the Empirical formula of Cysteine.

20. The taste of sour milk is due to Lactic Acid. The percentage composition of lactic Acid by mass is 40% carbon, 6.71% Hydrogen, and 53.29 % Oxygen. The molar mass of Lactic acid is 90 g. Find the Empirical and Molecular Formula of Lactic Acid.

21. A compound contains 12.8% carbon and 2.13% Hydrogen, the rest being Bromine atoms. The Molecular mass of the compound is 188 g. Calculate the Empirical and Molecular formula of the compound

22. Insects of a particular species are able to identify their mate by using special chemicals called pheromones that transmit chemical messages. The pheromone that serves as a sex attractant for gypsy moths is called disparlure, and contains thew elements C, H, and O. Analysis of disparlure shows that .282 g of the attractant contains 1.6 x 10-2 g of O atoms and 0.228 g of C atoms. The Mr of Disparlure is 282 g. determine the molecular formula of the compound.

23. Ethylene glycol is a compound often used as an anti-freeze in cars in cold weather. Its Molar mass is 62 g. it has a percentage composition of 38.7% Carbon, 9.7% Hydrogen, and the rest Oxygen. Determine both the Empirical and Molecular formula of this compound.

24. The active ingredient in photographic fixer solution contains Sodium, Sulphur, and Oxygen. Analysis of the Compound shows that it contains 0.979 g of Na, 1.365 g of S, and 1.021 of O. What is the Empirical formula for this compound?v

LIMITING REAGENT

25. Consider the reaction:

2 H2(g) + O2(g) ( 2 H2O(g)

Identify the limiting reagent in each of the reaction mixtures given below;

a) 50 molecules of H2 and 50 molecules of O2.

b) 100 molecules of H2 and 40 molecules of O2.

c) 100 molecules of H2 and 60 molecules of O2.

d) 0.50 moles of H2 and 0.75 moles of O2.

e) 0.80 moles of H2 and 0.75 moles of O2.

f) 1.0 g of H2 and 0.25 g of O2.

g) 5.0 g of H2 and 56 g of O2.

26. Magnesium and Chlorine react together according to the following equation;

Mg(s) + Cl2(g) ( MgCl2(s)

If 20.0 g of Magnesium and 20.0 g of Chlorine are available for a reaction, determine:

a) The limiting reagent.

b) the mass of MgCl2 formed

27. Hydrazine is used in rocket fuel. It reacts with Oxygen according to the equation below

N2H4(l) + O2(g) ( N2(g) + 2 H2O(g)

In a particular rocket engine, 2.29 g of hydrazine and 3.14 g of Oxygen are available to react.

a) Find the limiting reagent

b) Determine the mass of unreacted reagent that will be left after the reaction

c) Calculate the mass of water produced.

28. When a mixture of Silver metal and Sulphur is heated, Silver Sulphide is formed:

16 Ag(s) + S8(s) ( 8 Ag2S(s)

a) What mass of Silver Sulphide is produced from a mixture of 2.0 g of Silver and 2.0 g of Sulphur?

b) What mass of reactant is left unreacted?

29. Ammonia (NH3) is produced from the reaction between Nitrogen (N2) and Hydrogen (H2).

a) What is the maximum mass of ammonia that can be produced from a mixture of 1 X103 g N2 and 5 x 102 g H2?

b) what mass, of which starting material, will be left over?

PERCENTAGE YIELD

30. The reaction of ethane gas (C2H6) with chlorine gas (Cl2) produces C2H5Cl as it’s main product, along with HCl. In addition, the reaction invariably produces a variety of other minor products. Naturally the production of these other chemicals reduces the yield of the main product. Calculate the percentage yield of C2H5Cl if the reaction of 300 g of Ethane with 650 g of Chlorine produces 490 g of C2H5Cl.

31. Commercial brass, an alloy of Zn and Cu, reacts with Hydrochloric acid as follows:

Zn(s) + 2 HCl(aq) ( ZnCl2(aq) + H2(g)

Cu does not react with the Hydrochloric acid. When 0.5065 g of a certain Brass alloy is reacted with excess hydrochloric acid, 0.0985 g of ZnCl2 is eventually produced.

a) What is the composition (%Zn and %Cu) by mass?

b) how could this result be checked without changing the above procedure?

32. A 0.423 g sample of impure Sodium Nitrate was heated, converting all the Sodium Nitrate to 0.2864 g of Sodium Nitrite and Oxygen gas. Determine the percent of sodium Nitrate in the original sample.

33. Using the equation: 2 H2S + SO2 ( 2 H2O + 3 S

What is the percent yield if 10.5 g of Sulfur is produced when 6.4 g of H2S reacts in an excess of SO2?

COMPLEX REASONING PROCESS

34. What volume of CO2 gas is produced at S.T.P. when 20 g of Calcium Carbonate is heated? Assume the reaction yield is 100%

35. 100 g of Hydrochloric acid is added to 100 g of Zinc metal. What volume of gas is formed from this reaction at 25oC and 1 atm pressure?

36. An element X forms both a dichloride (XCl2) and a tetrachloride (XCl4). Treatment of 10.0 g of XCl2 with excess Chlorine forms 12.55 g of XCl4. Assuming the reaction had a 100% yield, calculate the atomic mass of X. Which element is it?

37. Nitric acid is produced commercially by the ostwald process, represented by the following equations;

4 NH3(g) + 5 O2(g) ( 4 NO(g) + 6 H2O(g)

2 NO(g) + O2(g) ( 2 NO2(g)

3 NO2(g) + H2O(l) ( 2 HNO3(aq) + NO(g)

What mass of NH3 must be used to produce 1 x 106 g of HNO3 by the Ostwald process?

38. The fuel is a disposable cigarette lighter is an unknown hydrocarbon, CxHy. When 1.5 g of CxHy is burnt in excess oxygen gas, 4.55 g of Carbon dioxide and 2.33 g of Water are produced.

a) Write an balanced equation (using x and y) to represent this combustion.

b) Deduce the empirical formula of CxHy

39. A compound contains only Carbon, Hydrogen, and Oxygen. Combustion of 10.68 g of the compound yields 16.01 g of Carbon dioxide and 4.37 g of Water. The molar mass of the compound is 176.1 g. What are the Empirical and Molecular formulas of the compound?

40. Lead (II) Sulphide (PbS) is precipitated when Hydrogen Sulphide (H2S) gas is passed into a solution of Lead (II) Nitrate (PbNO3).

Pb2+(aq) + H2S(g) ( PbS(s) + 2 H+(aq)

What mass of Lead (II) Nitrate was dissolved in the water if 4.796 g of Lead (II) Sulphide is precipitated? Assume a 100% yield for the reaction.

42. An oxide of Copper is heated in a stream of Hydrogen until only the copper remains. The data for the experiment is given below. Calculate the Empirical formula for the copper oxide.

| Mass of crucible |= 27.002 g |

|Mass of crucible plus contents before heating |= 27.128 g |

|Mass of cucible and contents after heating |= 27.114 g |

43. The production capacity for Acrylonitrile (C3H3N) in the United States of America is over one billion kilos per year. Acrylonitrile, the building block for making ployacrylonitrile fibres and a variety of plastics, is produced from gaseous propylene (C3H6), ammonia (NH3), and oxygen.

2 C3H6(g) + 2 NH3(g) + 3 O2(g) ( 2 C3H3N(g) + 6 H2O(g)

a) Assuming a 100% yield, what mass of acrylonitrile can be produced from a mixture of 500 g propylene, 500 g ammonia, and 1000 g of oxygen?

b)What mass of water is produced, and what masses of starting reagents are left over?

44. At constant temperature and pressure, a mixture of one litre of Carbon Monoxide and one litre of Oxygen is reacted to produce Carbon Dioxide. Find the volume of the mixture after the reaction.

45. You are given two 500 mL flasks, each filled with a different gas, both at S.T.P. One flask contains an unknown gas, and the other flask contains Nitrogen gas. Explain how you would go about determining the molecular mass of the unknown gas.

46. 0.22 g of an unknown gas is found to occupy 0.112 litres at S.T.P. What is the molar mass of the gas? What is the name of the gas?

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Assume 100% yield in each step of the reaction

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