Last updated on Oct 23, 2026

Amounts of Substances in Equations (OCR GCSE Chemistry A, Combined (Gateway Science Suite)): Quizzes

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Amounts of Substances in Equations

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What do the numbers in front of formulas in a balanced equation show?

The ratio of moles of each substance

In $Mg + 2HCl \rightarrow MgCl_2 + H_2$ , how many moles of $HCl$ react with 1 mole of $Mg$ ?

2 moles

In $Mg + 2HCl \rightarrow MgCl_2 + H_2$ , what is the mole ratio of $HCl$ to $H_2$ ?

2:1

What formula is used to calculate moles from mass?

Moles = mass ÷ Mr

How many moles are in 6g of $Mg$ if the Mr of $Mg$ is 24?

0.25 moles

What do you divide the mass by to calculate moles?

Mr or Ar

In $Mg + 2HCl \rightarrow MgCl_2 + H_2$ , how many moles of $H_2$ are produced from 1 mole of $Mg$ ?

1 mole

Why are mole ratios from balanced equations useful?

To calculate amounts needed or produced

How many moles are in 12g of $Mg$ if the Mr of $Mg$ is 24?

0.5 moles

In $Mg + 2HCl \rightarrow MgCl_2 + H_2$ , how many moles of $MgCl_2$ form from 1 mole of $Mg$ ?

1 mole

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Measurement, Mass & Equations

Calculating Mass of Substances

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Measurement, Mass & Equations

Calculating Mass of Substances

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Measurement, Mass & Equations

Calculating Mass of Substances

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Measurement, Mass & Equations

Calculating Mass of Substances

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