1.
What is a chemical reaction? State four distinct physical observations that help us to determine whether a chemical reaction has taken place.
2.
Why is a chemical change considered a permanent change whereas a physical change is temporary? Give one example of each to justify your answer.
3.
Write the balanced chemical equation representing the reaction between copper oxide and dilute hydrochloric acid. State the color change observed.
4.
When quicklime (calcium oxide) is added to water, a sizzling sound is heard and the container becomes extremely hot. Identify the type of reaction and write its chemical equation.
5.
Lead nitrate powder is heated in a dry boiling tube. State the observations, the color of the gas evolved, and the balanced chemical equation representing the thermal decomposition.
6.
A student added zinc granules to dilute sulphuric acid in a conical flask. What gas is evolved? How will you test this gas? Write the balanced chemical equation for the reaction.
7.
Explain why food items containing fats and oils are flushed with nitrogen gas before packaging. What is the role of antioxidants in this context?
8.
State the characteristics of the chemical reaction that occurs when:
- Dilute hydrochloric acid is added to sodium carbonate powder.
- Potassium iodide solution is added to lead nitrate solution.
9.
What happens chemically when quicklime is slaked with water? Write a balanced chemical equation and state whether it is an exothermic or endothermic process.
10.
Describe an activity to show that carbon dioxide gas is released during the burning of candle wax. Write the observations when the evolved gas is passed through lime water.
11.
State the Law of Conservation of Mass. Why is it essential to balance a chemical equation in accordance with this law?
12.
Balance the following chemical equation step-by-step: $\text{Fe}(s) + \text{H}_2\text{O}(g) \rightarrow \text{Fe}_3\text{O}_4(s) + \text{H}_2(g)$.
13.
Write balanced chemical equations for the following word equations:
- Hydrogen gas combines with nitrogen to form ammonia gas.
- Hydrogen sulphide gas burns in air to give water and sulphur dioxide gas.
14.
Balance the following equation: $\text{HNO}_3 + \text{Ca(OH)}_2 \rightarrow \text{Ca(NO}_3)_2 + \text{H}_2\text{O}$.
15.
Balance the following equation: $\text{NaOH} + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{SO}_4 + \text{H}_2\text{O}$.
16.
Balance the following equation: $\text{NaCl} + \text{AgNO}_3 \rightarrow \text{AgCl} + \text{NaNO}_3$.
17.
Balance the following equation: $\text{BaCl}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{BaSO}_4 + \text{HCl}$.
18.
Write a balanced chemical equation with state symbols for the following reaction: Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
19.
Balance the equation representing aerobic respiration: $\text{C}_6\text{H}_{12}\text{O}_6(aq) + 6\text{O}_2(g) \rightarrow 6\text{CO}_2(g) + 6\text{H}_2\text{O}(l) + \text{Energy}$.
20.
Balance the equation representing thermal decomposition of lead nitrate: $\text{Pb(NO}_3)_2(s) \xrightarrow{\Delta} \text{PbO}(s) + \text{NO}_2(g) + \text{O}_2(g)$.
21.
Balance the equation representing thermal decomposition of ferrous sulphate: $\text{FeSO}_4(s) \xrightarrow{\Delta} \text{Fe}_2\text{O}_3(s) + \text{SO}_2(g) + \text{SO}_3(g)$.
22.
Balance the following reaction: $\text{H}_2\text{S}(g) + \text{O}_2(g) \rightarrow \text{SO}_2(g) + \text{H}_2\text{O}(l)$.
23.
Balance the following displacement reaction: $\text{Al}(s) + \text{CuCl}_2(aq) \rightarrow \text{AlCl}_3(aq) + \text{Cu}(s)$.
24.
Explain the significance of state symbols in a chemical equation. Give an example where their omission could lead to incorrect thermodynamic interpretation.
25.
Balance the combustion of propane gas: $\text{C}_3\text{H}_8(g) + \text{O}_2(g) \rightarrow \text{CO}_2(g) + \text{H}_2\text{O}(g)$.
26.
Define a combination reaction. Give two examples: one between two elements, and another between an element and a compound.
27.
Why are decomposition reactions called the opposite of combination reactions? Explain with balanced chemical equations representing both reaction types.
28.
What is thermal decomposition? Write the balanced chemical equation for the thermal decomposition of calcium carbonate, stating its practical applications in industries.
29.
Describe an activity to demonstrate the electrolysis of water. Write the chemical equation involved and explain why the volume of gas collected at one electrode is double that of the other.
30.
What is photolytic decomposition? Give two examples of compounds that undergo decomposition in the presence of sunlight. Write their balanced chemical equations.
31.
Why are silver chloride bottles made of dark-colored glass? Write the reaction that takes place when silver chloride is exposed to light.
32.
Define displacement reaction. Why does the blue color of copper sulphate solution fade when an iron nail is dipped in it? Write the equation.
33.
Arrange Iron, Copper, and Zinc in increasing order of their reactivity based on displacement reactions. Support your answer with chemical equations.
34.
What happens when copper powder is heated in a china dish? State the color change and write the balanced chemical equation.
35.
When copper is exposed to moist air for a long time, it acquires a green coating. Identify the green compound formed and explain the chemical process.
36.
Differentiate between exothermic and endothermic reactions. Write one balanced equation for each type.
37.
Why is respiration considered an exothermic reaction? Explain the cellular process and write the glucose combustion equation.
38.
Why is the decomposition of vegetable matter into compost considered an exothermic reaction? How is it useful for farming?
39.
Write the chemical equation for the reaction of magnesium ribbon with nitrogen gas when burned in a nitrogen atmosphere. What is the name of the product?
40.
What is a neutralization reaction? Classify it under the broad types of reactions and give a balanced equation.
41.
What happens when sodium hydrogen carbonate is heated? Write the balanced chemical equation.
42.
A shiny brown colored element 'X' on heating in air becomes black in color. Name the element 'X' and the black colored compound formed. Write the balanced equation.
43.
Why do we apply paint on iron articles? Explain the chemical principle behind it.
44.
Name two antioxidants commonly used to prevent the rancidity of food materials.
45.
Write a balanced chemical equation for a decomposition reaction where energy is supplied in the form of electricity.
46.
Define oxidation and reduction in terms of gain or loss of oxygen.
47.
In terms of electronic concept (loss or gain of electrons), define oxidation and reduction with suitable examples.
48.
In the redox reaction $\text{CuO}(s) + \text{H}_2(g) \xrightarrow{\Delta} \text{Cu}(s) + \text{H}_2\text{O}(l)$, identify:
- The substance oxidized,
- The substance reduced,
- The oxidizing agent,
- The reducing agent.
49.
What is a Redox reaction? Demonstrate that the extraction reaction $\text{ZnO}(s) + \text{C}(s) \rightarrow \text{Zn}(s) + \text{CO}(g)$ is a redox process by identifying the oxidation and reduction steps.
50.
Define an oxidizing agent in terms of oxygen transfer. Identify the oxidizing agent in the reaction: $\text{H}_2\text{S}(g) + \text{Cl}_2(g) \rightarrow \text{2HCl}(g) + \text{S}(s)$.
51.
Identify the reducing agent in the reaction: $\text{Fe}_2\text{O}_3(s) + \text{3CO}(g) \rightarrow \text{2Fe}(s) + \text{3CO}_2(g)$.
52.
When aqueous solutions of barium chloride and sodium sulphate are mixed, a rapid reaction occurs. Write down the observations, the name of the precipitate formed, and the balanced equation.
53.
Are all double displacement reactions precipitation reactions? Give a balanced equation of a double displacement reaction that is a neutralization reaction instead of a precipitation reaction.
54.
Explain the oxidation of magnesium ribbon in air. Write down the oxidizing agent and the reducing agent in this reaction.
55.
In the reaction $\text{MnO}_2(s) + \text{4HCl}(aq) \rightarrow \text{MnCl}_2(aq) + \text{2H}_2\text{O}(l) + \text{Cl}_2(g)$, identify the substance that is oxidized and the substance acting as the oxidizing agent.
56.
Define corrosion. State the conditions necessary for the rusting of iron. Write the chemical formula of rust.
57.
Explain three distinct methods used to prevent the corrosion of metals (especially iron).
58.
What is rancidity? What are the environmental factors that accelerate rancidity in oily food items?
59.
Identify the substance oxidized and reduced in the following reaction: $4\text{Na}(s) + \text{O}_2(g) \rightarrow 2\text{Na}_2\text{O}(s)$.
60.
Write the balanced chemical equation for the reaction between hydrogen sulphide and sulphur dioxide: $2\text{H}_2\text{S} + \text{SO}_2 \rightarrow 3\text{S} + 2\text{H}_2\text{O}$. Identify the oxidizing and reducing agents.
A student set up the apparatus for the electrolysis of water. Acidified water was taken in a beaker, and two carbon electrodes were immersed. On passing electric current, gases were evolved at both electrodes and collected in test tubes.
61.
Based on Case Study 1, answer the following:
- Why is a few drops of dilute sulphuric acid added to pure water during electrolysis?
- At which electrode (anode or cathode) is hydrogen gas evolved?
- What is the ratio of gases collected at the anode and cathode by volume?
During the industrial extraction of iron from its oxide ore, the reaction takes place in a blast furnace. The following chemical step represents the extraction process: $\text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2$.
62.
Based on Case Study 2, answer the following:
- Which substance is reduced in this extraction reaction?
- Identify the reducing agent that facilitates this extraction.
- Why is carbon monoxide preferred over carbon in this step of the furnace?
A colorless and odorless gas 'X' is passed through lime water, which turns milky. On passing excess of gas 'X' into the same solution, the milkiness disappears.
63.
Based on the description above, answer the following:
- Identify the gas 'X'.
- Write balanced chemical equations for both chemical steps involved.
- What is the chemical name of the compound responsible for the disappearance of the milkiness?
An old copper coin was dipped in silver nitrate solution in a glass beaker. After some time, the student observed that the solution turned blue and a shiny silver coating appeared on the coin.
64.
Based on Case Study 3, answer the following:
- Explain the chemical reaction with a balanced equation.
- Identify the type of reaction representing this process.
- Why did the color of the solution change from colorless to blue?
A reddish-brown metal 'A' does not react with dilute hydrochloric acid. When heated in air in a china dish, it forms a black compound 'B'. Compound 'B' reacts with dilute sulphuric acid to form a blue colored solution 'C'.
65.
Based on the chemical changes described above, answer the following:
- Identify metal 'A' and compound 'B'.
- Write balanced chemical equations for all the reactions involved.
- What type of reaction is the formation of 'B' from 'A'?
For joining railway tracks on-site, a mixture of iron(III) oxide and aluminium powder is ignited. This reaction releases a massive amount of heat, and iron is obtained in molten form: $\text{Fe}_2\text{O}_3(s) + 2\text{Al}(s) \rightarrow 2\text{Fe}(l) + \text{Al}_2\text{O}_3(s) + \text{Heat}$.
66.
Based on Case Study 4, answer the following:
- What is the special name given to this displacement reaction?
- Why is iron obtained in liquid state rather than solid state in this reaction?
- Identify the substance oxidized and the oxidizing agent.
A chips manufacturing company was receiving complaints that their potato chips tasted stale and smelled bad after a few weeks of packaging.
67.
Analyze the complaint and answer the following:
- What chemical phenomenon is responsible for the stale taste and smell?
- Suggest the gas that should be filled in the packet during packaging to prevent this.
- Explain how this gas prevents the potato chips from turning stale.
A student heated lead nitrate in a boiling tube and observed brown fumes being evolved with a crackling sound.
68.
Based on Case Study 5, answer the following:
- Identify the brown gas evolved.
- Write the balanced chemical equation for the thermal decomposition of lead nitrate.
- What other gaseous product is formed during this decomposition? How will you test it?
Anhydrous copper sulphate is white. When a few drops of water are added to it, it turns blue and the container becomes warm.
69.
Based on the observation, answer the following:
- Write the chemical equation for the hydration of copper sulphate.
- Why does the container become warm?
- Is this reaction exothermic or endothermic? Justify.
An iron window frame in a coastal city like Mumbai rusted much faster than an identical window frame in a dry desert city like Jodhpur.
70.
Based on Case Study 6, answer the following:
- Explain the chemical process of rusting with its balanced equation.
- Why does rusting occur faster in coastal areas?
- Suggest two preventive measures to protect coastal window frames from rusting.
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