Homework: Reacting masses worksheet (42 Marks) Name: ___________________ Before starting this homework read CI 1.3 and add to your notes as necessary.

Question 1:

The equation below represents the thermal decomposition of potassium chlorate, KClO3.

2KClO3 (s) 2KCl(s) + 3O2(g)

Calculate the mass of oxygen which could be produced by the complete decomposition of 1.47 g

of KClO3.

answer = ............................... g [2]

Question 2:

Calculate the mass of H2O required to react completely with 5.0 g of SiCl4:

SiCl4 + 2H2O SiO2 + 4HCl

mass ............................... g [2]

Question 3: Solid Magnesium oxide reacts with water to produce magnesium hydroxide.

a. Write a balanced equation for the reaction.

......................................................................................................................... [1]

b. How many grams of MgO are needed to produce 264g of Mg(OH)2?

mass MgO ............................... g [2]

c. How many grams of magnesium hydroxide are produced when 57.0g of water are used?

mass Mg(OH)2............................... g [2]

d. How many grams of water are needed to react completely with 10.0g of magnesium oxide?

mass H2O ............................... g [2]

Question 4: A student made some calcium hydroxide by heating calcium carbonate and then adding water: CaCO3 CaO + CO2 then: CaO + H2O Ca(OH)2

Calculate the mass of calcium carbonate that the student would need to produce 10.0g of calcium hydroxide. Give your answer to 3 significant figures.

answer = ............................... kg [3]

Question 5:

When copper (II) nitrate is heated, it decomposes according to the following equation:

2Cu(NO3)2(s) 2CuO(s) + 4NO2(g) + O2(g)

When 20.0g of copper(II) nitrate is heated, a. What mass of copper(II) oxide would be produced?

answer = ............................... g [2]

b. What mass of NO2 would be produced?

answer = ............................... g [2]

Question 6: An iron ore (500 tonnes) contained 12% iron oxide (Fe2O3) by mass. The iron oxide was reduced

in the blast furnace to form iron: Fe2O3 (s) + 3CO(g) 2Fe(l) + 3CO2(g). (1 tonne = 1 x 106g)

(i) Calculate the mass of iron oxide (Fe2O3) found in the 500 tonnes of iron ore.

mass of iron oxide = ............................... tonnes [2]

(ii) How many moles of iron oxide (Fe2O3) were present?

moles of iron oxide = ............................... moles [2]

(iii) What mass of iron can be formed from this quantity of ore?

mass of iron = ............................... tonnes [2]

Question 7: A student reacted 1.44 g of titanium with chlorine to form 5.70 g of a chloride X.

(i) How many moles of Ti atoms reacted? [2]

(ii) How many moles of Cl atoms reacted? [2]

(iii) Determine the empirical formula of X. [2]

(iv) Write a balanced equation for the reaction between titanium and chlorine.

......................................................................................................................... [1]

Question 8: Use the equation below to calculate the mass of dinitrogen tetroxide that will combine with

25 g of methylhydrazine. Give your answer to two significant figures.

4CH3NHNH2(l) + 5N2O4(l) 4CO2(g) + 12H2O(l) + 9N2(g)

mass = .......................................g [3]

Question 9: Oil paintings in which white lead has been used can be blackened by reaction with H2S from air

pollution or from the glaze over the painting itself. The blackening comes from the formation of

lead sulphide, which may be cleaned off by washing with hydrogen peroxide, H2O2. The reaction

for the cleaning process is:

PbS (black solid) + 4H2O2(aq) PbSO4(s) + 4H2O(l)

a. How many grams of H2O2 must be used to clean off 0.24g of PbS?

mass = .......................................g [2]

b. If 0.072 g of H2O forms in the reaction, how many grams of PbSO4 must also have been formed?

mass = .......................................g [2]

Question 10: Antimony is found naturally in a number of minerals including stibnite. Stibnite typically contains 5% of Sb2S3. Antimony can be obtained by reducing Sb2S3 with scrap iron.

Sb2S3+ 3Fe 2Sb + 3FeS

(i) How many moles of Sb2S3 are in 500 kg of a typical sample of stibnite containing 5% by mass of Sb2S3? Use molar mass of Sb2S3 = 340 gmol-1; Ar: S = 32; Sb = 122

mol [2]

(ii) Calculate the mass of antimony that could be obtained by processing 500 kg of stibnite.

mass = kg [2]