10th grade chemical reactions, acids and bases

Question 1

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

Answer 

Question 2

How is gold usually obtained?

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

Question 3

Self-heating cans for camping use a reaction between calcium oxide and water. What type of reaction is this?

• A. electrolysis
• B. thermal decomposition
• C. endothermic
• D. exothermic

Question 4

What mass of glucose is needed to make 400 cm³ of solution with a concentration of 20 g/dm³, in g?

Answer g

Question 5

Alkenes and cracking: which statement is NOT true?

• A. Ethene can be used to make the polymer poly(ethene).
• B. Cracking makes longer molecules from shorter ones.
• C. Alkenes are more reactive than alkanes.
• D. Alkenes contain a carbon–carbon double bond.

Question 6

What is true at dynamic equilibrium?

• A. The forward and reverse reactions happen at the same rate
• B. There are equal amounts of reactants and products
• C. Only the forward reaction happens
• D. Both reactions have stopped

Question 7

20 g of copper sulfate is dissolved in water to make 500 cm³ of solution. What is the concentration, in g/dm³? (1 dm³ = 1000 cm³)

Answer g/dm³

Question 8

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

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

Question 9

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 10

Reactants: 110 kJ. Peak of the profile: 260 kJ. Products: 80 kJ. What is the activation energy, in kJ?

Answer kJ

Question 11

Why do refineries crack long-chain hydrocarbons?

• A. Long chains are too useful
• B. To remove all the carbon
• C. To make crude oil
• D. There is more demand for shorter chains such as petrol, and alkenes make polymers

Question 12

12.5 g of sodium hydroxide is dissolved to make 2.5 dm³ of solution. What is the concentration, in g/dm³?

Answer g/dm³

Question 13

Marble chips and acid were placed on a balance. The mass fell from 162.4 g to 160.6 g in 150 s as carbon dioxide escaped. What was the mean rate of reaction, in g/s? Give 3 decimal places.

Answer g/s

Question 14

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 15

Volume of gas collected: 0 s: 0 cm³; 20 s: 44 cm³; 40 s: 64 cm³; 60 s: 73 cm³; 80 s: 77 cm³; 100 s: 79 cm³. What was the mean rate between 0 s and 40 s, in cm³/s? Give 2 decimal places.

Answer cm³/s

Question 16

Bioleaching uses bacteria to extract copper. What is a drawback?

• A. It needs huge amounts of electricity
• B. It only works on gold
• C. It releases large amounts of carbon monoxide
• D. It is slow and can produce toxic leachate