CIE iGCSE Co-ordinated Sciences-C9.4 Reactivity series- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-C9.4 Reactivity series – Study Notes
CIE iGCSE Co-ordinated Sciences-C9.4 Reactivity series – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- State the order of the reactivity series as: potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, gold
- Describe the reactions, if any, of:
(a) potassium, sodium and calcium with cold water
(b) magnesium with steam
(c) magnesium, zinc, iron, copper, silver and gold with dilute hydrochloric acid and explain these reactions in terms of the position of the metals in the reactivity series - Deduce an order of reactivity from a given set of experimental results
Supplement
- Describe the relative reactivities of metals in terms of their tendency to form positive ions, by displacement reactions, if any, with the aqueous ions of magnesium, zinc, iron, copper and silver
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Reactivity Series of Metals
The reactivity series is a list of metals arranged in order of their reactivity, which is mainly determined by their tendency to lose electrons and form positive ions. The higher a metal is in the series, the more reactive it is.
Order of Reactivity (Most to Least):
Potassium > Sodium > Calcium > Magnesium > Aluminium > Carbon > Zinc > Iron > Hydrogen > Copper > Silver > Gold
Key Points:
- Metals at the top, like potassium and sodium, react very vigorously with water and acids because they lose electrons easily to form positive ions.
- Metals in the middle, such as zinc and iron, are moderately reactive and react slowly with acids or steam.
- Metals at the bottom, like copper, silver, and gold, are much less reactive and may not react at all with water or dilute acids under normal conditions.
- Hydrogen is included to show which metals can displace it from acids. Metals above hydrogen in the series will react with acids to produce hydrogen gas, whereas metals below hydrogen will not.
Example
Explain why potassium is more reactive than magnesium.
▶️Answer/Explanation
Potassium is higher in the reactivity series and has a single electron in its outermost shell, which it loses very easily to form K⁺ ions. Magnesium is lower in the series, with two electrons in its outer shell, and loses them less readily. Therefore, potassium reacts more vigorously than magnesium.
Example
Why does gold not react with dilute hydrochloric acid?
▶️Answer/Explanation
Gold is at the bottom of the reactivity series, meaning it has very little tendency to lose electrons and form ions. As a result, it does not react with dilute acids under normal conditions.
Relative Reactivity of Metals
The reactivity of a metal is mainly determined by its tendency to lose electrons and form positive ions (cations). Metals higher in the reactivity series form ions more readily and can displace ions of less reactive metals from their compounds in displacement reactions.
Displacement Reactions:
A more reactive metal can displace a less reactive metal from its aqueous solution of ions:
- \( \text{Mg (s) + Cu}^{2+} \text{(aq)} \rightarrow \text{Mg}^{2+} \text{(aq) + Cu (s)} \)
- \( \text{Zn (s) + Fe}^{2+} \text{(aq)} \rightarrow \text{Zn}^{2+} \text{(aq) + Fe (s)} \)
Less reactive metals cannot displace more reactive metals from their ions:
- \( \text{Cu (s) + Zn}^{2+} \text{(aq)} \text{→ No reaction} \)
Key Points:
- Magnesium, zinc, and iron are moderately reactive and can displace less reactive metals like copper, silver, and gold from their compounds.
- Metals above hydrogen in the series can react with acids to produce hydrogen gas, while metals below hydrogen cannot.
- The tendency to form positive ions explains the observed displacement reactions and the relative position of metals in the reactivity series.
Example
Explain the Reaction of magnesium with copper sulfate solution.
▶️Answer/Explanation
Magnesium is more reactive than copper. It displaces copper from copper sulfate:
\( \text{Mg (s) + CuSO}_4 \text{(aq)} \rightarrow \text{MgSO}_4 \text{(aq) + Cu (s)} \)
Copper precipitates out as solid while magnesium forms magnesium ions in solution.
Example
Explain the Reaction of copper with zinc sulfate solution.
▶️Answer/Explanation
Copper is less reactive than zinc, so it cannot displace zinc from zinc sulfate. No reaction occurs:
\( \text{Cu (s) + ZnSO}_4 \text{(aq)} \rightarrow \text{No reaction} \)
Reactions of Metals with Water, Steam, and Dilute Acids
The reactivity of metals can be observed through their reactions with water, steam, and acids. The position of a metal in the reactivity series determines the nature and vigour of these reactions.
Reaction with cold water:
Highly reactive metals like potassium, sodium, and calcium react vigorously with cold water to form hydroxides and hydrogen gas:
- \( 2\text{K} + 2\text{H}_2\text{O} \rightarrow 2\text{KOH} + \text{H}_2 \)
- \( 2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2 \)
- \( \text{Ca} + 2\text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{H}_2 \)
Reaction with steam:
Metals like magnesium react slowly with steam to produce metal oxides and hydrogen:
- \( \text{Mg} + \text{H}_2\text{O (g)} \rightarrow \text{MgO} + \text{H}_2 \)
Reaction with dilute acids:
Metals above hydrogen in the reactivity series react with acids to produce a salt and hydrogen gas:
- \( \text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2 \)
- \( \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2 \)
- \( \text{Fe} + 2\text{HCl} \rightarrow \text{FeCl}_2 + \text{H}_2 \)
- Less reactive metals like copper, silver, and gold do not react with dilute acids under normal conditions.
Explanation in terms of reactivity series:
- Highly reactive metals (top of the series) lose electrons easily and react vigorously with water or acids.
- Moderately reactive metals (middle of the series) react slowly, often requiring heat or steam.
- Less reactive metals (bottom of the series) do not react with water or dilute acids because they do not lose electrons readily.
Example
Explain the Reaction of sodium with cold water.
▶️Answer/Explanation
Sodium reacts vigorously with water to produce sodium hydroxide and hydrogen gas:
\( 2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2 \)
The reaction is exothermic and produces fizzing hydrogen gas.
Example
Explain the Reaction of magnesium with dilute hydrochloric acid.
▶️Answer/Explanation
Magnesium reacts slowly with dilute HCl to form magnesium chloride and hydrogen:
\( \text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2 \)
The reaction is less vigorous than sodium or calcium with water because magnesium is lower in the reactivity series.
Example
Explain the Reaction of copper with dilute hydrochloric acid.
▶️Answer/Explanation
Copper is below hydrogen in the reactivity series, so it does not react with dilute acids. No hydrogen gas is produced, and the solution remains unchanged.
Deduce the Order of Reactivity from Experimental Results
The reactivity of metals can be compared experimentally by observing their reactions with water, steam, acids, or solutions of other metal ions. By noting which metals react more vigorously or displace other metals, an order of reactivity can be deduced.
Key Observations for Deduction:
- A metal that reacts more vigorously with water, steam, or acid is more reactive.
- A metal that displaces another metal from its solution is more reactive than the metal being displaced.
- Metals that do not react with water, steam, or acids, or cannot displace other metals, are less reactive.
Example:
Given experimental observations:
- Magnesium reacts faster with HCl than zinc.
- Zinc reacts with copper sulfate solution to form copper.
- Copper does not react with zinc sulfate solution.
From these results, the relative order of reactivity is: Magnesium > Zinc > Copper.
Example
Explain the Displacement reactions to determine reactivity
▶️Answer/Explanation
Zinc reacts with copper sulfate to form zinc sulfate and copper:
\( \text{Zn (s) + CuSO}_4 \text{(aq)} \rightarrow \text{ZnSO}_4 \text{(aq) + Cu (s)} \)
Copper cannot displace zinc from zinc sulfate, so zinc is more reactive than copper.
Example
Explain the Reaction with acids to compare reactivity
▶️Answer/Explanation
Magnesium reacts faster with dilute hydrochloric acid than zinc:
\( \text{Mg + 2HCl → MgCl}_2 + \text{H}_2 \)
\( \text{Zn + 2HCl → ZnCl}_2 + \text{H}_2 \) (slower)
This shows magnesium is more reactive than zinc.