Chemical Reactions Quiz For Grade 8

The given balanced equation is 2H2 + _O2 -> 2H2O. This equation is balanced because there are equal numbers of atoms on both sides of the equation. On the left side, there are 4 hydrogen atoms (2 from each H2 molecule) and 2 oxygen atoms (from the O2 molecule). On the right side, there are also 4 hydrogen atoms (2 from each H2O molecule) and 2 oxygen atoms (from the 2H2O molecules). Therefore, the equation is balanced.

This is a double replacement reaction. In this type of reaction, the cations and anions of two different compounds switch places, resulting in the formation of two new compounds. In the given example, sodium chloride (NaCl) reacts with silver nitrate (AgNO3) to form sodium nitrate (NaNO3) and silver chloride (AgCl).

A single replacement reaction occurs when one element replaces another in a compound. In this type of reaction, a more reactive element displaces a less reactive element from its compound. This results in the formation of a new compound and a different element. Single replacement reactions are also known as substitution reactions.

When a compound breaks down, it undergoes a decomposition reaction. In this type of reaction, a compound is broken down into simpler substances or elements. This can occur through various processes such as heat, light, or the addition of a catalyst. Decomposition reactions are commonly observed in nature and can be seen in processes like decay, digestion, and the breakdown of organic matter.

Burning wood is an example of combustion because it involves a chemical reaction between the wood and oxygen, resulting in the release of heat and light energy. Combustion is a process in which a substance reacts with oxygen to produce heat and often flames, which is exactly what happens when wood is burned.

This reaction is a single replacement reaction because it involves one element or ion being replaced by another element or ion in a compound. In single replacement reactions, one element is always displaced from a compound while another element takes its place.

In the given reaction, methane (CH4) reacts with oxygen (O2) to form carbon dioxide (CO2) and water (H2O). This is a combustion reaction where methane, a hydrocarbon, is oxidized in the presence of oxygen to produce carbon dioxide and water as the products. Therefore, the correct answer is Carbon Dioxide and Water.

Synthesis is the opposite of decomposition because it involves the combination of two or more substances to form a more complex substance. In contrast, decomposition is the breakdown of a compound into simpler substances. Therefore, synthesis and decomposition are opposite reactions in terms of the direction of the chemical change.

When the negative ions in two compounds switch, it indicates a double-replacement reaction. In this type of reaction, the positive ions remain unchanged, but the negative ions exchange places. This reaction typically occurs when two ionic compounds react in an aqueous solution, resulting in the formation of two new compounds. The double-replacement reaction is characterized by the formation of a precipitate, gas, or water as a product.

An example of a synthesis reaction is when hydrogen and oxygen combine to form water (2H2 + O2 -> 2H2O). In this reaction, two molecules of hydrogen gas react with one molecule of oxygen gas to produce two molecules of water. This is a synthesis reaction because it involves the combination of simpler substances (hydrogen and oxygen) to form a more complex substance (water).

The given chemical reaction is a single replacement reaction. In this reaction, zinc (Zn) reacts with hydrochloric acid (HCl) to form zinc chloride (ZnCl2) and hydrogen gas (H2). In a single replacement reaction, one element replaces another element in a compound, resulting in the formation of a new compound and a different element.

When a metal bubbles when placed in an unknown liquid, it indicates that a chemical reaction has taken place. Bubbling is often a result of a gas being released during a reaction. In this case, the metal is reacting with the unknown liquid to produce gas, causing the bubbling effect. This is a clear indication that a chemical reaction has occurred.

The given reaction, Mg + 2OH -> Mg(OH)2, is an example of a synthesis reaction. In a synthesis reaction, two or more reactants combine to form a single product. In this case, magnesium (Mg) reacts with two hydroxide ions (OH) to form magnesium hydroxide (Mg(OH)2). This reaction follows the general form A + B -> AB, where A and B are the reactants and AB is the product.

Decomposition is the correct answer because it is a type of reaction that involves the breakdown of a compound into two or more simpler substances. In this type of reaction, there is only one reactant that undergoes decomposition to form multiple products. This is in contrast to single replacement and synthesis reactions, which involve multiple reactants combining or replacing each other.