Chemistry: Predicting Products in Single Displacement Reactions

Understanding Single Displacement Reactions 🧪

A single displacement reaction (also known as a single replacement reaction) occurs when one element replaces another in a compound. The general form is:

$A + BC \rightarrow AC + B$

Where A, B, and C are elements. To predict whether a single displacement reaction will occur, we use the activity series.

The Activity Series 🥇🥈🥉

The activity series is a list of elements ordered by their relative reactivity. Metals are listed in order of decreasing ease of oxidation, and halogens are listed in order of decreasing ease of reduction. An element can only replace another element below it in the activity series.

Activity Series of Metals (Example)

• Li
• K
• Ba
• Ca
• Na
• Mg
• Al
• Zn
• Fe
• Ni
• Sn
• Pb
• H₂
• Cu
• Ag
• Au

Activity Series of Halogens (Example)

• F₂
• Cl₂
• Br₂
• I₂

Steps to Predict Products 📝

1. Identify the Reactants: Determine the element and the compound involved in the reaction.
2. Consult the Activity Series: Find the element in the activity series.
3. Determine if Displacement Occurs: Check if the element is higher in the series than the element it might replace in the compound. If yes, the reaction occurs; otherwise, no reaction.
4. Predict the Products: If the reaction occurs, write the new compound and the displaced element.
5. Balance the Equation: Ensure the equation is balanced to satisfy the law of conservation of mass.

Example 1: Zinc and Copper(II) Sulfate 🔩

Reaction: $Zn(s) + CuSO_4(aq) \rightarrow ?$

1. Zinc (Zn) and Copper(II) Sulfate ($CuSO_4$) are the reactants.
2. Zinc is above Copper (Cu) in the activity series.
3. Since Zinc is more reactive than Copper, it will displace Copper.
4. Products: Zinc Sulfate ($ZnSO_4$) and Copper (Cu).
5. Balanced Equation: $Zn(s) + CuSO_4(aq) \rightarrow ZnSO_4(aq) + Cu(s)$

Example 2: Copper and Magnesium Chloride 🚫

Reaction: $Cu(s) + MgCl_2(aq) \rightarrow ?$

1. Copper (Cu) and Magnesium Chloride ($MgCl_2$) are the reactants.
2. Copper is below Magnesium (Mg) in the activity series.
3. Since Copper is less reactive than Magnesium, it will not displace Magnesium.
4. No Reaction: $Cu(s) + MgCl_2(aq) \rightarrow$ No Reaction

Example 3: Fluorine and Sodium Chloride 💡

Reaction: $F_2(g) + NaCl(aq) \rightarrow ?$

1. Fluorine ($F_2$) and Sodium Chloride ($NaCl$) are the reactants.
2. Fluorine is above Chlorine (Cl) in the halogen activity series.
3. Since Fluorine is more reactive than Chlorine, it will displace Chlorine.
4. Products: Sodium Fluoride ($NaF$) and Chlorine ($Cl_2$).
5. Balanced Equation: $F_2(g) + 2NaCl(aq) \rightarrow 2NaF(aq) + Cl_2(g)$

Important Notes ⚠️

• Hydrogen (H₂) is included in the metal activity series because many acids react with metals to produce hydrogen gas.
• The activity series is an empirical tool, meaning it's based on observation rather than theoretical calculation.