Chapter 4 Reacting masses, and chemical equations - Pre 8

A molecule contains carbon, hydrogen and oxygen. For every carbon atom there are twice as many hydrogen atoms but the same number of oxygen atoms. What is the formula of the molecule?

• C₂H₆O

• C₂H₄O₂

• C₄H₈O₂

• C₂H₂O₂

Theobromine is a stimulant found in chocolate and in tea leaves and is closely related to caffeine, the stimulant found in coffee.

What is the formula of theobromine?

• C₆H₅N₄O₂

• C₇H₈N₄O₂

• C₇H₈N₃O₂

• C₇H₇N₄O₃

Hydrogen reacts with elements from Group VII to produce compounds called hydrogen halides. An example is when a molecule of hydrogen reacts with a molecule of fluorine to produce hydrogen fluoride. What is the correct equation for the reaction?

• 2 H + 2 F → 2 HF

• H₂ + F₂ → H₂F₂

• 2 H + 2 F → H₂F₂

• H₂ + F₂ → 2 HF

Leucine is an essential amino acid used in the synthesis of proteins in the body.

What is the relative molecular mass of leucine?

• 144 g

• 86 g

• 125 g

• 131 g

When magnesium carbonate is heated, the products are magnesium oxide and carbon dioxide. What mass of magnesium oxide is formed when 21 g of magnesium carbonate thermally decomposes?

(A_r : Mg = 24, C = 12, O = 16)

• 22

• 10

• 11

• 20

What is the balanced equation for the reaction of methane and oxygen?

• CH₄(g) + 2 O₂(g) → CO₂(g) + H₂O(g)

• CH₄(g) + O₂(g) → CO₂(g) + 2 H₂O(g)

• 2 CH₄(g) + 4 O₂(g) → 2 CO₂(g) + H₂O(g)

• CH₄(g) + 2 O₂(g) → CO₂(g) + 2 H₂O(g)

A compound contains two atoms of oxygen and one atom of calcium. It also contains hydrogen in sufficient amounts so that the overall charge of the molecule is neutral. What is the molecular formula for the compound?

• Ca(OH)₄

• Ca(OH)₂

• H₄CaO₂

• CaO₂H₂

Dilute sulfuric acid and barium chloride solution react to produce barium sulfate and hydrochloric acid, as shown in the reaction below:

H₂SO₄ + BaCl₂ → BaSO₄ + 2 HCl

Which row represents the correct state symbols for the reaction?

• A

• B

• C

• D

6 g of hydrogen react with 48 g of oxygen to form water. A chemist performs the same reaction using 2 g of hydrogen. What mass of oxygen is required to combine with the hydrogen?

• 24 g

• 12 g

• 16 g

• 72 g

The table shows the name and formula of common ionic compounds formed from the ions.

Which row is not correct?

• lithium sulfide

  Li₂S

• Iron(II) fluoride

  Fe₂F₃

• Aluminium sulfate Al₂(SO₄)₃

• Magnesium nitrate Mg(NO₃)₂