7th grade chemical reactions, acids and bases

Question 1

In a sealed flask, 13 g of substance A reacts completely with 32 g of substance B. 9 g of product D forms along with product C. What mass of C forms, in g?

Answer g

Question 2

Copper carbonate is heated strongly and breaks down. What are the products?

• A. copper + carbon dioxide
• B. copper hydroxide + water
• C. copper oxide + carbon dioxide
• D. copper + oxygen + carbon

Question 3

When 100 g of calcium carbonate is heated, it forms 56 g of calcium oxide and 44 g of carbon dioxide. What mass of carbon dioxide forms from 10 g of calcium carbonate, in g?

Answer g

Question 4

Complete the word equation: zinc + oxygen → ___

• A. magnesium oxide
• B. zinc oxide
• C. zinc chloride
• D. zinc carbonate

Question 5

Universal indicator results: milk pH 6, oven cleaner pH 13, pure water pH 7, lemon juice pH 2. Which is the most alkaline?

• A. lemon juice
• B. milk
• C. oven cleaner
• D. pure water

Question 6

Acids and alkalis: which statement is NOT true?

• A. All acids are dangerous.
• B. Alkalis are bases that dissolve in water.
• C. Acids have a pH below 7.
• D. Pure water has a pH of 7.

Question 7

Universal indicator turns red in a solution. What does this tell you?

• A. It is a strong alkali
• B. It is a strong acid
• C. It is pure water
• D. It is neutral

Question 8

A solution has a pH of 14. What colour will universal indicator turn?

• A. blue
• B. purple
• C. orange or yellow
• D. red

Question 9

Combustion: which statement is NOT true?

• A. Combustion is a reaction with oxygen that releases energy.
• B. Burning fossil fuels releases carbon dioxide.
• C. Hydrogen burns to make only water.
• D. A fire can burn without oxygen.

Question 10

5 g of calcium carbonate is heated in an open tube until it all breaks down. 2.8 g of calcium oxide is left. What mass of carbon dioxide escaped, in g?

Answer g

Question 11

Word equations: which statement is NOT true?

• A. Burning metal makes it lighter because mass is lost.
• B. Reactants are written on the left of the arrow.
• C. Incomplete combustion can produce carbon monoxide, a poisonous gas.
• D. Combustion is a reaction with oxygen.

Question 12

Complete the word equation: aluminium + oxygen → ?

Answer 

Question 13

Why is limestone (calcium carbonate) heated in kilns?

• A. to turn it into gold
• B. to make oxygen
• C. to make it heavier
• D. to make quicklime (calcium oxide) for cement and building

Question 14

Blue litmus paper is dipped into lemon juice. What happens?

• A. It stays blue
• B. It turns red
• C. It turns purple
• D. It turns green

Question 15

Magnesium ribbon is burned in a crucible. The ash weighs more than the ribbon did. Why?

• A. Heat has mass
• B. The crucible got heavier
• C. Burning creates new atoms
• D. Oxygen atoms from the air have combined with the magnesium

Question 16

Why is a gas boiler with a poor air supply dangerous?

• A. It stops producing heat completely
• B. It makes the water too pure
• C. Incomplete combustion produces toxic carbon monoxide
• D. It produces too much oxygen