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9th grade chemical reactions, acids and bases

9th grade (Year 10 in England) · 14 questions · Common Core: NGSS.MS-PS1-5, NGSS.HS-PS1-7, NGSS.HS-PS1-5, NGSS.HS-PS1-2 · England: KS4 Combined Science: Chemical changes, KS4 Combined Science: The rate and extent of chemical change, KS3 Chemistry: Chemical reactions

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1
Question 1
A gas puts out a lighted splint and turns limewater milky. What is it?
- A. carbon dioxide
- B. oxygen
- C. hydrogen
- D. chlorine
Question 2
A reaction produces 20 cm³ of gas in 10 seconds. What is the mean rate of reaction, in cm³/s?
Answercm³/s
Question 3
4Fe + 3O₂ → 2Fe₂O₃ How many Fe atoms are on the right side of this balanced equation?
Answer
4
Question 4
Why is crude oil called a finite (non-renewable) resource?
- A. It is made in factories
- B. It never runs out
- C. It formed over millions of years and is used much faster than it forms
- D. It is made from sunlight each day
5
Question 5
Iron is extracted from iron oxide by heating it with carbon. Why does this work?
- A. Carbon is more reactive than iron, so it removes the oxygen
- B. Iron is more reactive than carbon
- C. Heat alone splits iron oxide
- D. Carbon is a metal
6
Question 6
Why does powdered marble react faster with acid than marble chips?
- A. Powder is a different substance
- B. Chips are hotter
- C. Powder has a larger surface area, so there are more collisions
- D. Powder has more mass
7
Question 7
Which gas gives this result: bubbled through limewater, it turns it milky?
- A. hydrogen
- B. oxygen
- C. carbon dioxide
- D. chlorine
8
Question 8
Rates of reaction: which statement is NOT true?
- A. A catalyst is not used up in a reaction.
- B. Food lasts longer in a fridge because reactions are slower at low temperature.
- C. Every collision between particles causes a reaction.
- D. Reactions need particles to collide with enough energy.
Question 9
Alkanes have the general formula CₙH₂ₙ₊₂. How many hydrogen atoms are in an alkane with 7 carbon atoms?
Answer
10
Question 10
Tests for gases: which statement is NOT true?
- A. Chlorine may turn damp blue litmus red before bleaching it.
- B. Hydrogen gives a squeaky pop with a lighted splint.
- C. Chlorine turns limewater milky.
- D. Oxygen relights a glowing splint.
11
Question 11
A flame test gives a crimson flame. Which metal ion is present?
- A. potassium, K⁺
- B. sodium, Na⁺
- C. copper, Cu²⁺
- D. lithium, Li⁺
12
Question 12
Why can a flame test be hard to use for a mixture of sodium and potassium compounds?
- A. Potassium does not give a flame colour
- B. The bright yellow sodium flame can hide the lilac potassium colour
- C. Mixtures cannot be heated
- D. The colours combine into green
Question 13
Balance the equation. What number goes in the gap? CH₄ + __O₂ → CO₂ + 2H₂O
Answer
14
Question 14
Sodium hydroxide solution is added to a solution and a white precipitate forms. Which metal ion is present?
- A. copper(II), Cu²⁺
- B. iron(II), Fe²⁺
- C. iron(III), Fe³⁺
- D. calcium, magnesium or aluminium ions

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Answer key: 9th grade chemical reactions, acids and bases

1. A. carbon dioxide
2. 2 cm³/s
3. 4
4. C. It formed over millions of years and is used much faster than it forms
5. A. Carbon is more reactive than iron, so it removes the oxygen
6. C. Powder has a larger surface area, so there are more collisions
7. C. carbon dioxide
8. C. Every collision between particles causes a reaction.
9. 16
10. C. Chlorine turns limewater milky.
11. D. lithium, Li⁺
12. B. The bright yellow sodium flame can hide the lilac potassium colour
13. 2
14. D. calcium, magnesium or aluminium ions