Chemistry Practice Questions (Continued)
Chemistry Practice Questions
1. In which of the following mixtures will there be reaction?
A) Silver metal with calcium nitrate solution
B) Magnesium with copper(II) nitrate
Write the balanced equation for any reaction that occurs. What observations are expected for A) and B)?
2. Bronze is a mixture of copper and tin metals. Draw a labeled diagram to show the arrangement of atoms in bronze.
3(a) Nitrogen monoxide, NO, is an atmospheric pollutant.
One source of nitrogen monoxide is from the gases from car engines.
Explain how nitrogen monoxide is formed in a car engine and indicate how its emission can be limited.
Formation :
Limiting its formation :
(b) Nitrogen monoxide can react with oxygen to form nitrogen dioxide. Write a balanced equation for the reaction.
(c) Why is nitrogen dioxide an atmospheric pollutant?
3. A gas jar at room temperature contains 2 moles of chlorine gas and 1 mole of hydrogen gas.
(a) The gases are allowed to react together at a higher temperature. Write the equation for the reaction that takes place.
(b) Name the gases which will be present in the gas jar after the reaction.
(c) Moist red and blue litmus papers are introduced into the jar. Describe the colour change(s) to the litmus papers.
4. Water and hydrogen peroxide are important compounds of hydrogen.
(a) Write the chemical formulae of water and hydrogen peroxide.
(b) What is the oxidation number of hydrogen in hydrogen peroxide?
(c) What are the products when hydrogen peroxide is allowed to decompose slowly?
(d) Describe the colour change when acidified potassium manganate(VII) is added to hydrogen peroxide.
(e) What happens to the arrangement and movement of the molecules in water as water is cooled from 25oC to -6oC?
6. A student has a bottle of sulfuric acid and a bottle of potassium hydroxide. He mixed the contents of the two bottles together.
(a) Write the equation for the reaction.
(b) Aqueous barium nitrate is added to the resultant mixture of potassium hydroxide and sulfuric acid. What is the name of the white precipitate formed?
7. An element, symbol E, forms an ionic oxide E3+ O2-. Predict, giving your reasons,
(a) whether E is a metal or a non-metal,
(b) in which group of the Periodic Table element E is found.
(c) Does the molten oxide of E conduct electricity.
8. Iodine and sodium sulfate are both crystalline solids at room temperature.
(a) Identify one difference in the structures of these two solids.
(b) Explain why these two solids have very different melting points.
(c) Describe the colours of iodine and solid sodium sulfate.
9. Excess chlorine gas is bubbled into two separate solutions of litmus and potassium bromide.
(a) State the colour of chlorine gas.
(b) Describe the colour changes in the two solutions.
10. Bromoethane can be made by reacting ethane with bromine.
C2H6 + Br2 --> C2H5Br + Substance Y
(a) Name substance Y.
(b) What is the type of reaction?
(c) What conditions are required for this reaction?
11. During cracking, nonane, C9H20 produces two different products: butane and substance Y.
C9H20 -->C4H10 + product Y
What is product Y?
Answers:
1. A) No reaction. B) Displacement reaction occurs.
A) No visible observation.
B) Mg + Cu(NO3)2 -> Cu + Mg(NO3)2
The solution turns from blue to colourless. A pink deposit of copper is observed.
2. Refer to your textbook. Tin, being bigger atoms than copper, are found in between copper atoms.
3(a) Nitrogen gas and oxygen gas combine at very high temperature in the car engine to form nitrogen monoxide. The catalytic converter of the car engine can convert NO into N2 gas.
(b) 2NO + O2 -> 2NO2
(c) It dissolves in rain water to form acid rain. Acid rain can destroy vegetation.
3(a) H2 + Cl2 -> 2HCl
(b) Chlorine gas is in excess. Hydrogen chloride and chlorine gas are present after reaction.
(c) The red litmus will be bleached. The blue litmus will turn red and will be bleached.
4(a) Water : H2O; Hydrogen peroxide : H2O2
(b) H in H2O2: +1
(c) Products are water and oxygen gas.
(d) Potassium manganate(VII) oxidises hydrogen peroxide to oxygen gas. It will be turned from purple to colourless.
(e) 25oC to 0oC : The liquid molecules of water are closely packed together. They are able to move about. At 0oC, water is frozen to ice. From 0oC to -60oC, the ice molecules are arranged in a lattice structure and can only vibrate about their fixed positions.
6(a) H2SO4 + 2KOH -> K2SO4 +_2H2O
(b) White precipitate : barium sulfate.
7(a) E is a metal. E atom loses 3 valence electrons to form E3+ ions. Metal atoms usually lose valence electrons to form ionsw.
(b) E is found in Group III
(c) Molten oxide of E contains mobile ions which can conduct electricity.
8(a) Between iodine molecules are weak Van der Waals’ forces. Strong electrostatic forces of attraction exist between the ions of sodium sulfate.
(b) The weak Van der Waals’ forces of attraction between iodine molecules require little energy to overcome. Hence it has low melting point. It requires a lot of energy to overcome the ionic bonds in sodium sulfate. Hence, it has high melting point.
9(a) Chlorine gas is greenish – yellow.
(b) Litmus is turned to red and it later bleaches. A reddish brown precipitate of bromine is observed between chlorine and potassium bromide.
10(a) Y is hydrogen bromide.
(b) Type of reaction: substitution. (Free radical substitution)
(c) uv light or strong heating.
11. Y is C5H10.
1. In which of the following mixtures will there be reaction?
A) Silver metal with calcium nitrate solution
B) Magnesium with copper(II) nitrate
Write the balanced equation for any reaction that occurs. What observations are expected for A) and B)?
2. Bronze is a mixture of copper and tin metals. Draw a labeled diagram to show the arrangement of atoms in bronze.
3(a) Nitrogen monoxide, NO, is an atmospheric pollutant.
One source of nitrogen monoxide is from the gases from car engines.
Explain how nitrogen monoxide is formed in a car engine and indicate how its emission can be limited.
Formation :
Limiting its formation :
(b) Nitrogen monoxide can react with oxygen to form nitrogen dioxide. Write a balanced equation for the reaction.
(c) Why is nitrogen dioxide an atmospheric pollutant?
3. A gas jar at room temperature contains 2 moles of chlorine gas and 1 mole of hydrogen gas.
(a) The gases are allowed to react together at a higher temperature. Write the equation for the reaction that takes place.
(b) Name the gases which will be present in the gas jar after the reaction.
(c) Moist red and blue litmus papers are introduced into the jar. Describe the colour change(s) to the litmus papers.
4. Water and hydrogen peroxide are important compounds of hydrogen.
(a) Write the chemical formulae of water and hydrogen peroxide.
(b) What is the oxidation number of hydrogen in hydrogen peroxide?
(c) What are the products when hydrogen peroxide is allowed to decompose slowly?
(d) Describe the colour change when acidified potassium manganate(VII) is added to hydrogen peroxide.
(e) What happens to the arrangement and movement of the molecules in water as water is cooled from 25oC to -6oC?
6. A student has a bottle of sulfuric acid and a bottle of potassium hydroxide. He mixed the contents of the two bottles together.
(a) Write the equation for the reaction.
(b) Aqueous barium nitrate is added to the resultant mixture of potassium hydroxide and sulfuric acid. What is the name of the white precipitate formed?
7. An element, symbol E, forms an ionic oxide E3+ O2-. Predict, giving your reasons,
(a) whether E is a metal or a non-metal,
(b) in which group of the Periodic Table element E is found.
(c) Does the molten oxide of E conduct electricity.
8. Iodine and sodium sulfate are both crystalline solids at room temperature.
(a) Identify one difference in the structures of these two solids.
(b) Explain why these two solids have very different melting points.
(c) Describe the colours of iodine and solid sodium sulfate.
9. Excess chlorine gas is bubbled into two separate solutions of litmus and potassium bromide.
(a) State the colour of chlorine gas.
(b) Describe the colour changes in the two solutions.
10. Bromoethane can be made by reacting ethane with bromine.
C2H6 + Br2 --> C2H5Br + Substance Y
(a) Name substance Y.
(b) What is the type of reaction?
(c) What conditions are required for this reaction?
11. During cracking, nonane, C9H20 produces two different products: butane and substance Y.
C9H20 -->C4H10 + product Y
What is product Y?
Answers:
1. A) No reaction. B) Displacement reaction occurs.
A) No visible observation.
B) Mg + Cu(NO3)2 -> Cu + Mg(NO3)2
The solution turns from blue to colourless. A pink deposit of copper is observed.
2. Refer to your textbook. Tin, being bigger atoms than copper, are found in between copper atoms.
3(a) Nitrogen gas and oxygen gas combine at very high temperature in the car engine to form nitrogen monoxide. The catalytic converter of the car engine can convert NO into N2 gas.
(b) 2NO + O2 -> 2NO2
(c) It dissolves in rain water to form acid rain. Acid rain can destroy vegetation.
3(a) H2 + Cl2 -> 2HCl
(b) Chlorine gas is in excess. Hydrogen chloride and chlorine gas are present after reaction.
(c) The red litmus will be bleached. The blue litmus will turn red and will be bleached.
4(a) Water : H2O; Hydrogen peroxide : H2O2
(b) H in H2O2: +1
(c) Products are water and oxygen gas.
(d) Potassium manganate(VII) oxidises hydrogen peroxide to oxygen gas. It will be turned from purple to colourless.
(e) 25oC to 0oC : The liquid molecules of water are closely packed together. They are able to move about. At 0oC, water is frozen to ice. From 0oC to -60oC, the ice molecules are arranged in a lattice structure and can only vibrate about their fixed positions.
6(a) H2SO4 + 2KOH -> K2SO4 +_2H2O
(b) White precipitate : barium sulfate.
7(a) E is a metal. E atom loses 3 valence electrons to form E3+ ions. Metal atoms usually lose valence electrons to form ionsw.
(b) E is found in Group III
(c) Molten oxide of E contains mobile ions which can conduct electricity.
8(a) Between iodine molecules are weak Van der Waals’ forces. Strong electrostatic forces of attraction exist between the ions of sodium sulfate.
(b) The weak Van der Waals’ forces of attraction between iodine molecules require little energy to overcome. Hence it has low melting point. It requires a lot of energy to overcome the ionic bonds in sodium sulfate. Hence, it has high melting point.
9(a) Chlorine gas is greenish – yellow.
(b) Litmus is turned to red and it later bleaches. A reddish brown precipitate of bromine is observed between chlorine and potassium bromide.
10(a) Y is hydrogen bromide.
(b) Type of reaction: substitution. (Free radical substitution)
(c) uv light or strong heating.
11. Y is C5H10.
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