10th grade chemical reactions, acids and bases

Question 1

Extracting metals: which statement is NOT true?

• A. An ore is a rock containing enough metal to make extraction worthwhile.
• B. Life cycle assessments compare the environmental impact of products.
• C. Carbon can reduce zinc oxide to zinc.
• D. Aluminium can be extracted by heating its oxide with carbon.

Question 2

How is platinum usually obtained?

• A. electrolysis
• B. reduction with carbon
• C. found as the native metal

Question 3

0.8 g of copper sulfate is dissolved in water to make 200 cm³ of solution. What is the concentration, in g/dm³? (1 dm³ = 1000 cm³)

Answer g/dm³

Question 4

Why is extracting aluminium by electrolysis so expensive?

• A. The electrodes are made of gold
• B. Aluminium ore is very rare
• C. It needs huge amounts of electricity to melt the ore and drive the reaction
• D. Aluminium is less reactive than carbon

Question 5

Volume of gas collected: 0 s: 0 cm³; 20 s: 32 cm³; 40 s: 43 cm³; 60 s: 48 cm³; 80 s: 49 cm³; 100 s: 50 cm³. What was the mean rate between 40 s and 80 s, in cm³/s? Give 2 decimal places.

Answer cm³/s

Question 6

Magnesium reacted with acid and 20 cm³ of hydrogen was collected in 10 s. What was the mean rate of reaction, in cm³/s?

Answer cm³/s

Question 7

Electrolysis of sodium sulfate solution: what forms at the anode (positive electrode)?

• A. oxygen
• B. chlorine
• C. sulfur
• D. bromine

Question 8

All substances are gases in this equilibrium: 2SO₂ + O₂ ⇌ 2SO₃. The forward reaction is exothermic. Product is removed as it forms. What happens to the position of equilibrium?

• A. shifts right (more products)
• B. shifts left (more reactants)
• C. no change in position

Question 9

50 g of sodium hydroxide is dissolved to make 2 dm³ of solution. What is the concentration, in g/dm³?

Answer g/dm³

Question 10

On a reaction profile, the reactants are at 100 kJ, the peak is at 180 kJ and the products are at 70 kJ. What is the overall energy change, in kJ? (Use a minus sign if energy is released.)

Answer kJ

Question 11

Cracking: C₈H₁₈ → C₅H₁₂ + an alkene. How many carbon atoms are in one molecule of the alkene?

Answer 

Question 12

Marble chips and acid were placed on a balance. The mass fell from 120 g to 118.2 g in 200 s as carbon dioxide escaped. What was the mean rate of reaction, in g/s? Give 3 decimal places.

Answer g/s

Question 13

Equilibrium: which statement is NOT true?

• A. If a reversible reaction is exothermic in one direction, it is endothermic in the other.
• B. Equilibrium can only be reached in a closed system.
• C. A catalyst increases the yield at equilibrium.
• D. Changing the conditions can change the position of equilibrium.

Question 14

Which conditions are used for catalytic cracking?

• A. dissolving the oil in water
• B. adding acid at room temperature
• C. vaporised hydrocarbons passed over a hot catalyst
• D. freezing the oil

Question 15

Electrolysis of potassium bromide solution: what forms at the cathode (negative electrode)?

• A. hydrogen
• B. zinc
• C. aluminium
• D. silver

Question 16

Reactants: 90 kJ. Peak of the profile: 215 kJ. Products: 110 kJ. What is the activation energy, in kJ?

Answer kJ