A-Level AQA Chemistry Formulae, Equations & Calculations: The equation for the reaction be

The equation for the reaction between zinc and hydrochloric acid is Zn + 2HCl → ZnCl₂ + H₂ What is the minimum mass, in mg, of zinc (Ar = 85.4) needed to react with 50.0 cm³ of 1.68 mol dm⁻³ hydrochloric acid? - AQA - A-Level Chemistry - Question 19 - 2017 - Paper 3

Question 19

The equation for the reaction between zinc and hydrochloric acid is Zn + 2HCl → ZnCl₂ + H₂ What is the minimum mass, in mg, of zinc (Ar = 85.4) needed to react wit... show full transcript

Worked Solution & Example Answer:The equation for the reaction between zinc and hydrochloric acid is Zn + 2HCl → ZnCl₂ + H₂ What is the minimum mass, in mg, of zinc (Ar = 85.4) needed to react with 50.0 cm³ of 1.68 mol dm⁻³ hydrochloric acid? - AQA - A-Level Chemistry - Question 19 - 2017 - Paper 3

Step 1

Calculate the moles of hydrochloric acid

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Answer

To determine the moles of hydrochloric acid (HCl), we use the formula:

ext{Moles} = ext{Concentration} imes ext{Volume}

Given:

Concentration = 1.68 mol dm⁻³
Volume = 50.0 cm³ = 0.0500 dm³ (since 1000 cm³ = 1 dm³)

Now substituting the values:

ext{Moles HCl} = 1.68 imes 0.0500 = 0.084 ext{ mol}

Step 2

Determine the moles of zinc needed

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Answer

From the balanced equation:

ext{Zn} + 2 ext{HCl} ightarrow ext{ZnCl}_2 + ext{H}_2

This shows that 1 mole of zinc reacts with 2 moles of hydrochloric acid. Thus, the moles of zinc required can be calculated as:

ext{Moles Zn} = rac{0.084 ext{ mol HCl}}{2} = 0.042 ext{ mol Zn}

Step 3

Calculate the mass of zinc needed

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Answer

Using the atomic mass of zinc (Ar = 65.4 g/mol), the mass of zinc can be calculated using:

ext{Mass} = ext{Moles} imes ext{Molar Mass}

Substituting the values:

ext{Mass Zn} = 0.042 ext{ mol} imes 65.4 ext{ g/mol} = 2.748 ext{ g}

Since the answer is required in mg:

ext{Mass in mg} = 2.748 ext{ g} imes 1000 = 2748 ext{ mg}

Step 4

Final Answer

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Answer

The minimum mass of zinc needed is approximately 2.75 mg.

The equation for the reaction between zinc and hydrochloric acid is Zn + 2HCl → ZnCl₂ + H₂ What is the minimum mass, in mg, of zinc (Ar = 85.4) needed to react with 50.0 cm³ of 1.68 mol dm⁻³ hydrochloric acid? - AQA - A-Level Chemistry - Question 19 - 2017 - Paper 3

Calculate the moles of hydrochloric acid

Determine the moles of zinc needed

Calculate the mass of zinc needed

Final Answer

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