Question

1. name the type of reaction (synthesis, decomposition, single displacement, double displacement, or combustion) that occurs given the following evidence. (5 marks)

a) precipitate forms
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b) ch4 + o2 ⇒ co2 + h2o + energy
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c) fe + b ⇒ feb
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d) cl2 + kbr ⇒ kcl + br2
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e) production of gas
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1. indicate whether the following property belongs to an acid, base, or neutral (3 marks)

a) ionic compounds
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b) have a sour taste
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c) ph 4
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Explanation:

• Question 3a: In a double displacement reaction, the positive and negative ions of two ionic compounds exchange places. When a precipitate forms, it is a common outcome of a double displacement reaction where the new combination of ions is insoluble in the reaction medium.
• Question 3b: Combustion reactions involve a substance reacting with oxygen to produce carbon dioxide, water, and energy. Here, \(CH_4\) (methane) reacts with \(O_2\) (oxygen) to give \(CO_2\), \(H_2O\), and energy, which is characteristic of a combustion reaction.
• Question 3c: Synthesis reactions combine two or more reactants to form a single product. In the reaction \(Fe + B

ightarrow FeB\), two elements (\(Fe\) and \(B\)) combine to form a single compound (\(FeB\)), so it is a synthesis reaction.

• Question 3d: In a single displacement reaction, one element displaces another element from a compound. In \(Cl_2+KBr

ightarrow KCl + Br_2\), chlorine (\(Cl_2\)) displaces bromine (\(Br\)) from \(KBr\) (since chlorine is more reactive than bromine in this context), so it is a single displacement reaction.

• Question 3e: Decomposition reactions break down a single reactant into two or more products. The production of gas can be a result of a decomposition reaction. For example, \(H_2CO_3

ightarrow H_2O+CO_2\uparrow\) (carbonic acid decomposing into water and carbon dioxide gas).

• Question 4a: Ionic compounds can be formed from both acids and bases (e.g., salt - base reaction or acid - base neutralization). But if we consider the general property, bases often form ionic compounds more prominently in some of their reactions (e.g., metal hydroxides - ionic compounds). However, a more accurate way: many salts (which can be considered as products of acid - base reactions) are ionic. But if we have to choose between acid, base, and neutral, bases (metal hydroxides) are ionic compounds.
• Question 4b: Acids are known for having a sour taste. For example, citric acid in citrus fruits gives them a sour taste.
• Question 4c: The pH scale ranges from 0 - 14. A pH less than 7 indicates an acidic solution. Since \(pH = 4\lt7\), it belongs to an acid.

Answer:

• 3a) Double displacement
• 3b) Combustion
• 3c) Synthesis
• 3d) Single displacement
• 3e) Decomposition
• 4a) Base
• 4b) Acid
• 4c) Acid