Indicate what type, or types, of reaction each of the following represents:
(a) Ca(s) + Br2(l) —> CaBr2(s)
(b) Ca (OH)2 (aq) + 2HBr(aq) —> CaBr2(aq) + 2H2O(l)
c) C6H12 (l) + 9O2(g) —> 6CO2(g) + 6H2O(g)
The correct answer and explanation is :
Reactions and Types
Let’s analyze each reaction and determine what type of reaction it represents:
(a) Ca(s) + Br2(l) → CaBr2(s)
This is a synthesis (combination) reaction.
- Explanation: In a synthesis reaction, two or more reactants combine to form a single product. In this case, calcium (Ca), a solid, reacts with bromine (Br2), a liquid, to form calcium bromide (CaBr2), a solid ionic compound.
- The key feature of this reaction is the combination of calcium and bromine to form a single product, CaBr2. It involves the formation of ionic bonds between calcium and bromine atoms.
Type: Synthesis (combination) reaction.
(b) Ca(OH)2(aq) + 2HBr(aq) → CaBr2(aq) + 2H2O(l)
This is a double displacement (or metathesis) reaction and specifically, an acid-base neutralization.
- Explanation: In a double displacement reaction, two compounds exchange ions to form new compounds. Here, calcium hydroxide (Ca(OH)2), a base, reacts with hydrogen bromide (HBr), an acid. The hydroxide ion (OH⁻) from calcium hydroxide reacts with the hydrogen ion (H⁺) from hydrogen bromide to form water (H2O). The calcium ion (Ca²⁺) combines with the bromide ion (Br⁻) to form calcium bromide (CaBr2).
- This reaction is also a neutralization reaction because it involves an acid (HBr) and a base (Ca(OH)2) reacting to form water and an ionic salt (CaBr2).
Type: Double displacement reaction (acid-base neutralization).
(c) C6H12(l) + 9O2(g) → 6CO2(g) + 6H2O(g)
This is a combustion reaction.
- Explanation: In a combustion reaction, a hydrocarbon (or any compound containing carbon, hydrogen, and sometimes oxygen) reacts with oxygen gas to produce carbon dioxide and water. Here, C6H12 (a hydrocarbon, likely cyclohexane) reacts with oxygen (O2) to form carbon dioxide (CO2) and water (H2O).
- Combustion reactions are exothermic, meaning they release energy in the form of heat and light. In this case, the carbon in C6H12 is oxidized to form CO2, and the hydrogen is oxidized to form H2O.
Type: Combustion reaction.
Summary of Reaction Types:
- (a) Synthesis (combination) reaction.
- (b) Double displacement (neutralization) reaction.
- (c) Combustion reaction.
Each of these reactions involves different types of chemical processes: combination of elements to form a compound, an acid-base interaction resulting in water and a salt, and the burning of a hydrocarbon in oxygen to produce CO2 and H2O.