5 Most SAQ’s of Chemical Equations Chapter in Class 10th Physical Science (TS/AP)

4 Marks

SAQ-1 : Write the chemical equation of the reaction, when hydrogen react with oxygen and forms water. Balance the chemical equation.

Introduction

When hydrogen gas reacts with oxygen gas, water is formed as a product. The chemical equation for this reaction needs to be balanced to satisfy the Law of Conservation of Mass, which states that mass is neither created nor destroyed in a chemical reaction.

Balancing the Chemical Equation:

1. Unbalanced Chemical Equation:
   $$\mathrm{H_2 + O_2 \rightarrow H_2O}$$
   In the unbalanced equation, there are 2 hydrogen atoms on the left side and 2 on the right side, but there are 2 oxygen atoms on the left side and only 1 on the right side.
2. Balancing the Equation:
   To balance the equation, we can place a coefficient in front of H₂​O to balance the oxygen atoms:
   $$\mathrm{H_2 + O_2 \rightarrow 2H_2O}$$
   Now, there are 2 oxygen atoms on each side, but now there are 4 hydrogen atoms on the right side and only 2 on the left side. To balance the hydrogen atoms, place a coefficient of 2 in front of
   $$\mathrm{H_2}$$
   $$\mathrm{2H_2 + O_2 \rightarrow 2H_2O}$$
3. Balanced Chemical Equation:
   $$\mathrm{2H_2 + O_2 \rightarrow 2H_2O}$$
   So, two molecules of hydrogen gas react with one molecule of oxygen gas to form two molecules of water.

Summary

The reaction of hydrogen gas with oxygen gas to form water is represented by the balanced chemical equation 2H₂+O₂→2H₂O. Balancing this equation is essential to comply with the Law of Conservation of Mass and accurately reflect the stoichiometry of the reaction.

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SAQ-2 : Mention the physical states of the reactants and products of the following chemical reactions and balance the equations.
a) C₆H₁₂O₆→C₂H₅OH+CO₂ b) Na+H₂O→NaOH+H₂

Introduction

This guide provides an uncomplicated overview of two chemical reactions, presenting the physical states of reactants and products and balancing the equations for each reaction. This explanation is helpful for anyone looking to understand these chemical processes in a straightforward manner.

Chemical Reaction 1:

1. Reaction:
   $$C_6H_{12}O_6 \rightarrow C_2H_5OH + CO_2$$
2. Physical States:
   • C₆H₁₂O₆​ (solid) changes into C₂H₅OH (liquid) and CO₂​ (gas).
3. Balanced Equation:
   • $$C_6H_{12}O_6(s) \rightarrow 2C_2H_5OH(l) + 2CO_2(g)$$
   • In this reaction, solid glucose (C₆H₁₂O₆) is converted into liquid ethanol (C₂H₅OH) and gas carbon dioxide (CO₂​).

Chemical Reaction 2:

1. Reaction:
   $$Na + H_2O \rightarrow NaOH + H_2$$
2. Physical States:
   • Na (solid) and H₂​O (liquid) change into NaOH (aqueous) and H₂​ (gas).
3. Balanced Equation:
   • $$2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g)$$
   • In this second reaction, solid sodium (Na) reacts with liquid water (H₂​O) to form aqueous sodium hydroxide (NaOH) and gas hydrogen (H₂​).

Summary

This guide provides a clear and simple breakdown of two chemical reactions, showing the physical states of reactants and products along with the balanced equations. Understanding these aspects is essential for a clear grasp of chemical reactions.

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SAQ-3 : Write the balanced chemical equations for the following reactions.
a) Zinc + Silver nitrate → Zinc nitrate + Silver
b) Ammonium nitrate → Nitrous oxide + Water

Introduction

Below are two chemical reactions provided with their balanced chemical equations. Each equation is written following the Law of Conservation of Mass. It’s critical to balance chemical equations to represent the actual stoichiometry of the reaction, ensuring that the number and type of atoms on either side of the equation are equal.

Reaction 1: Zinc and Silver Nitrate

1. Unbalanced Equation:
   $$Zn + AgNO_3 \rightarrow Zn(NO_3)_2 + Ag$$
2. Balanced Equation:
   $$Zn + 2AgNO_3 \rightarrow Zn(NO_3)_2 + 2Ag$$
3. In this reaction, Zinc reacts with Silver Nitrate to form Zinc Nitrate and Silver. The balanced equation ensures that there are equal numbers of each atom on both sides of the equation, following the law of conservation of mass.

Reaction 2: Decomposition of Ammonium Nitrate

1. Unbalanced Equation:
   $$NH_4NO_3 \rightarrow N_2O + H_2O$$
2. Balanced Equation:
   $$2NH_4NO_3 \rightarrow 2N_2O + 4H_2O$$
3. Here, Ammonium Nitrate decomposes to form Nitrous Oxide and Water. The balanced equation ensures that the number of nitrogen, hydrogen, and oxygen atoms is equal on both sides of the equation.

Summary

This guide presented two balanced chemical equations for the reactions of Zinc with Silver Nitrate and the decomposition of Ammonium Nitrate. Balancing chemical equations is crucial for understanding the exact ratios of reactants and products involved in the reactions, ensuring adherence to the law of conservation of mass.

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SAQ-4 : i)CaCO₃(s)→CaO (s)+CO₂ (g) ii) 2AgBr (s)→2 Ag (s)+Br₂ (g)
Mention the types of reactions to which the above equations belong. Also mention, which of them is a photo chemical reaction.

Introduction

Understanding the type of chemical reactions is essential for the study and application of chemistry. This section examines two specific chemical reactions, identifying the type of each reaction. One of these reactions is further identified as a photochemical reaction, highlighting the role of light in the process.

Reaction 1: Decomposition of Calcium Carbonate

1. Equation:
   $$CaCO_3 (s) \rightarrow CaO (s) + CO_2 (g)$$
2. Type of Reaction:Decomposition Reaction
   In this reaction, calcium carbonate (a solid) breaks down into calcium oxide (also a solid) and carbon dioxide gas. This is a standard decomposition reaction where a single compound breaks down into two or more simpler substances.

Reaction 2: Decomposition of Silver Bromide

1. Equation:
   $$2AgBr (s) \rightarrow 2Ag (s) + Br_2 (g)$$
2. Type of Reaction:Photochemical Decomposition Reaction
   In this case, silver bromide, a solid, decomposes into silver (solid) and bromine (gas) in the presence of sunlight. This is a photochemical reaction, as it requires light to proceed.

Summary

This discussion explained two specific chemical reactions: the decomposition of calcium carbonate and silver bromide. The first is a straightforward decomposition reaction, while the second is a photochemical decomposition reaction, occurring only in the presence of light. Recognizing the types of reactions and the conditions under which they occur is crucial for a comprehensive understanding of chemistry.

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SAQ-5 : Observe the following balanced chemical equation and answer the given question

C₃ H₈ (g)+5O₂(g)→3CO₂(g)+4H₂O (g)

i. How many molecules of oxygen are involved in this chemical reaction?

ii.How many moles of propane are required to get 20 moles of water?

Introduction

The given balanced chemical equation C₃​H₈​(g)+5O₂​(g)→3CO₂​(g)+4H₂​O(g) represents the combustion of propane. By examining this equation, we can determine how many molecules of oxygen are involved and how many moles of propane are needed to produce a specific amount of water.

Molecules of Oxygen Involved:

1. Equation:
   $$C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(g)$$
2. Oxygen Molecules:5 molecules of O₂​
   According to the balanced equation, 5 molecules of oxygen are involved in the combustion of one molecule of propane.

Moles of Propane for Water Production:

1. Desired Water Moles: 20 moles of H₂​O
2. Required Propane Moles: To produce 20 moles of water, 5 moles of C₃​H₈​ are required.
   • From the equation, 1 mole of C₃​H₈​ produces 4 moles of H₂​O. Therefore, to produce 20 moles of water,
     $$\frac{20 \, \text{moles of } H_2O}{4 \, \text{moles of } H_2O \, \text{per mole of } C_3H_8} = 5 \, \text{moles of } C_3H_8$$

Summary

This analysis evaluated a given chemical equation for propane combustion. It was determined that 5 molecules of oxygen are involved in the reaction for each molecule of propane. Additionally, 5 moles of propane are necessary to produce 20 moles of water. These observations help to understand the stoichiometry and molecule involvement in chemical reactions.