Grade 10 Physical Sciences · Chemical Change

Define stoichiometry terms and laws

Give the exact meaning of words like mole, molar mass, concentration and limiting reagent, or state a law in full.

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The mole concept: What is a mole? Quantitative aspects of chemical changeMiss Martins Maths and Science

Empirical and Molecular formula: Chemistry | StoichiometryMiss Martins Maths and Science

Limiting Reagents and Percent YieldProfessor Dave Explains

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Question 7.1 · November 2025 · Paper 2 · Provincial · 2 marks

Learners crushed eggshells to determine the percentage of calcium carbonate that are found in a

1, 5

g sample. The crushed eggshells are allowed to react with EXCESS hydrochloric acid. The balanced equation for the reaction:

CaCO_{3} (s) + 2 HCl (aq) \to CaCl_{2} (aq) + CO_{2} (g) + H_{2} O (ℓ)

The calcium carbonate reacted completely in 5 minutes. The graph below shows the carbon dioxide gas that was collected at STP.

Calculate the: Diagram for this question

7.1 Define the term limiting reagent.(2)

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3. Question 6.3.1 · November 2025 · Paper 2 · Provincial · 2 marks
A certain organic compound ( $CxHyOz$ ) is composed of $54, 54$ g of carbon; $9, 1$ g of hydrogen and $36, 36$ g of oxygen and has a molecular mass of $88$ g·mol $^{- 1}$ .
6.3 A bottle in a laboratory contains an unknown metal hydroxide (MOH). A lab technician dissolves $1, 826$ g of the metal hydroxide to make a $100$ cm $^{3}$ solution.

Upon analysis it was found that the concentration of the metal hydroxide is $0, 326$ mol·dm $^{- 3}$ .

Answer the questions that follow.
6.3.1 Define the term concentration.(2)
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1. ✓
  Definition of concentrationThe amount of solute per litre of solution.
  2 marks · Define stoichiometry terms and laws
4. Question 6.2.1 · November 2024 · Paper 2 · Provincial · 2 marks
6.2 5 g of sodium carbonate ( $Na_{2} CO_{3}$ ) reacts with $250$ cm $^{3}$ of hydrochloric acid (HC $ℓ$ ).

$Na_{2} CO_{3} (s) + 2 HC ℓ (aq) \to 2 NaC ℓ (aq) + H_{2} O (ℓ) + CO_{2} (g)$

The percentage of hydrochloric acid (HC $ℓ$ ) that reacted with sodium carbonate ( $Na_{2} CO_{3}$ ) is $76$ %.
6.2.1 Define the term limiting reagent.(2)
Show the memo (1 tick)Memo
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  Definition of limiting reagentLimiting reagent is a reactant that is completely used up in a chemical reaction.
  2 marks · Define stoichiometry terms and laws
5. Question 5.1 · November 2023 · Paper 2 · Provincial · 2 marks
An unknown organic compound has a formula of $C_{x} H_{y} O_{z}$ . The molar mass of this compound is $88$ g·mol $^{- 1}$ .
5.1 Define the term empirical formula.(2)
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  Definition of empirical formulaThe simplest whole-number ratio of atoms in a compound.
  2 marks · Define stoichiometry terms and laws
6. Question 2.4.1 · November 2023 · Paper 2 · Provincial · 2 marks
Use the table of substances below to answer the following questions.
2.4 The experimental setup below is used to dry $10$ g hydrated blue copper(II) sulphate crystals, $CuSO_{4} \cdot x H_{2} O$ , to form $6, 4$ g anhydrous salt.

Answer the questions that follow.
2.4.1 Define term anhydrous.(2)
Show the memo (1 tick)Memo
1. ✓
  Definition of anhydrousFree of water.
  2 marks · Define stoichiometry terms and laws

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