Chemical Reactions

To solve this problem, we need to balance the chemical equation:

1. Given Reaction:
The unbalanced equation is:

2. Balancing the Equation:
- Sodium (Na) reacts with water (H₂O) to form sodium hydroxide (NaOH) and hydrogen gas (H₂).
- To balance, we start by balancing hydrogen (H). On the right side, there is 1 molecule of H₂, which provides 2 hydrogen atoms. Therefore, we need 2 NaOH on the left.
- Now, we balance sodium (Na). Since there are 2 sodium atoms in 2 NaOH, we need 2 sodium atoms on the left, i.e., 2 Na.
- Lastly, oxygen (O) is already balanced as it appears once on both sides.

3. The Balanced Equation:

4. Coefficient of Na:
The coefficient of Na (sodium) in the balanced equation is 2.

Final Answer:
The correct option is (A) 2.

To solve the problem, we need to identify the type of chemical reaction in which heat is absorbed.

1. Understanding the Types of Reactions:

- Oxidation reaction: Involves the loss of electrons, often accompanied by the release of heat. It is not a heat-absorbing reaction.
- Exothermic reaction: This type of reaction releases heat into the surroundings.
- Endothermic reaction: In this type of reaction, heat is absorbed from the surroundings to proceed, making it a heat-absorbing reaction.
- Reduction reaction: Involves the gain of electrons, but it does not inherently involve the absorption of heat.

2. Identifying the Correct Answer:
The correct type of reaction that absorbs heat is an *endothermic reaction.

Final Answer:
The correct answer is option (C): Endothermic reaction.

To solve this problem, we need to understand the chemical reaction that occurs during the Thermite process.

1. The Thermite Reaction:
The Thermite process involves a reaction between a metal oxide (usually iron(III) oxide) and a more reactive metal (typically aluminum). The reaction is highly exothermic and results in the reduction of the metal oxide and the production of molten metal. The reaction is as follows:

2. Nature of the Reaction:
In this reaction, aluminum (Al) reduces iron(III) oxide (Fe₂O₃) to produce iron (Fe), while aluminum is oxidized to form aluminum oxide (Al₂O₃). Therefore, the reaction is a reduction reaction.

3. Evaluating the Options:
(A) Reduction – Correct ✅ (The reaction involves the reduction of iron(III) oxide by aluminum.)
(B) Oxidation – Incorrect (Although oxidation occurs for aluminum, the overall reaction is reduction.)
(C) Neutralisation – Incorrect (Neutralisation is not involved in this reaction.)
(D) None of the above – Incorrect

Final Answer:
The correct option is (A) Reduction.

To solve the problem, we need to understand the meaning of the symbol "Δ" in a chemical equation.

1. Understanding the Symbol Δ:
In a chemical equation, the symbol "Δ" represents heating. It is used to indicate that the reaction occurs under the influence of heat.

2. Evaluate the Options:
- Option (A): Catalyst – The catalyst is typically written above or below the arrow, not represented by "Δ".
- Option (B): Precipitate – A precipitate is usually written as a product or reactant, not with "Δ".
- Option (C): Heating – This is correct, as "Δ" indicates that heat is applied during the reaction.
- Option (D): Physical state – Physical states of reactants/products are indicated by symbols like (s), (l), (g), or (aq), not "Δ".

Final Answer:
The correct answer is option (C): Heating.

To solve the problem, we need to identify the product formed when quick lime reacts with water.

1. Reaction of Quick Lime with Water:
Quick lime is calcium oxide (CaO). When calcium oxide reacts with water, it forms calcium hydroxide (Ca(OH)₂), also known as slaked lime.

2. The Chemical Equation:
The reaction is as follows:

Final Answer:
The product formed when quick lime reacts with water is Ca(OH)₂ (Option B).

To solve the problem, we need to understand the characteristics of an endothermic reaction.

1. Definition of Endothermic Reaction:
An endothermic reaction is a chemical reaction in which energy, specifically heat, is absorbed from the surroundings. This leads to a decrease in temperature in the immediate surroundings of the reaction.

2. Characteristics of Endothermic Reactions:
In an endothermic reaction, heat is absorbed from the surroundings in order to break bonds and facilitate the reaction. This is in contrast to exothermic reactions, where heat is released into the surroundings.

Final Answer:
In an endothermic reaction, heat is .

To solve the problem, we need to identify the type of reaction when acid is mixed with water.

1. Understanding the Reaction:
When an acid is added to water, it releases heat. This is because the dilution of the acid with water involves the breaking of bonds in the acid molecules, which releases energy in the form of heat. Therefore, this process is an exothermic reaction.

2. Verifying Other Options:

- Exothermic Reaction: This is the correct answer, as the reaction releases heat during the mixing of acid and water.
- Endothermic Reaction: This would involve heat being absorbed, which does not occur when acid is mixed with water.
- Neutralisation: This refers to the reaction between an acid and a base, not acid and water.

Final Answer:
Mixing acid with water is an .

To solve the problem, we need to identify the correct reagents that form bleaching powder.

1. Composition of Bleaching Powder:
Bleaching powder is a chemical compound with the formula . It is formed by the reaction of slaked lime (calcium hydroxide) with chlorine gas.

2. Analyzing the Options:

- Option (1): Slaked lime + HCl — This reaction produces calcium chloride and water, but not bleaching powder.
- Option (2): Slaked lime + Cl₂ — This is the correct reaction. Slaked lime reacts with chlorine gas to produce bleaching powder.
- Option (3): Quick lime + HCl — This reaction forms calcium chloride and water, not bleaching powder.
- Option (4): Quick lime + CO₂ — This reaction forms calcium carbonate, not bleaching powder.

Final Answer:
Bleaching powder is formed from Slaked lime + Cl₂ (Option B).

To solve the problem, we need to identify the compound formed when ethanol (CH₃CH₂OH) is heated with concentrated sulfuric acid (H₂SO₄) at 170°C.

1. Understanding the Reaction Conditions:
When alcohols are heated with concentrated sulfuric acid at high temperatures (~170°C), a dehydration reaction occurs, which removes a water molecule and forms an alkene.

2. Reaction Mechanism:
CH₃CH₂OH (ethanol) → CH₂=CH₂ (ethene) + H₂O
This is an example of an elimination reaction (E1 mechanism), where ethanol loses a water molecule to form ethene.

3. Eliminate Incorrect Options:
- (1) CH₃CHO → Ethanal (formed by mild oxidation, not dehydration)
- (2) CH₃–CH₃ → Ethane (not formed by dehydration)
- (3) CH₃COOH → Acetic acid (formed by complete oxidation)
- (4) CH₂=CH₂ → Ethene (correct product of dehydration of ethanol)

Final Answer:
The compound formed is CH₂=CH₂ (ethene).

To solve the problem, we need to identify the gas evolved when zinc (Zn) reacts with dilute hydrochloric acid (HCl).

1. Chemical Reaction:
When zinc reacts with dilute hydrochloric acid, it displaces hydrogen from the acid and forms zinc chloride and hydrogen gas:

2. Gas Released:
From the reaction, the gas evolved is (hydrogen gas).

Final Answer:
The gas formed is .