Chemical Reactions and Equations: Class 10 Chemistry Q&A · Page 5
120 free answers on Chemical Reactions and Equations (Chemistry) for Class 10 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- ChemistryClass 10ICSE
The chemical reaction between the two substances is characterised by a change in colour from orange to green. These two substances are most likely to be: (a) Potassium dichromate solution and sulphur dioxide (b) Potassium permanganate solution and sulphur dioxide (c) Potassium permanganate solution and lemon juice Potassium dichromate solution and carbon dioxide
Option (a) is the answer. Reaction between potassium dichromate and sulphur dioxide is characterised by change in colour. The orange colour of acidified potassium dichromate will change into green by passing sulphur dioxide
- ChemistryClass 10ICSE
An acid which can decolourise purple coloured potassium permanganate solution is : (a) Sulphuric acid (b) Citric acid (d) Carbonic acid (d) Hydrochloric acid
Option (b) is the answer. Reaction of purple-coloured potassium permanganate with citric acid is characterised by change in colour from purple to colourless
- ChemistryClass 10ICSE
You are given the solution of lead nitrate. In order to obtain a yellow precipitate you should mix it with a solution of (a) Potassium chloride (b) Potassium nitride (c) Potassium sulphide Potassium iodide
Option (d) is the answer. When a solution of lead nitrate reacts with potassium iodide it gives yellow precipitate of lead iodide
- ChemistryClass 10ICSE
Which one of the following does not involve a chemical reaction? (a) Digestion of food in our body (b) Process of respiration (c) Burning of candle wax when heated Melting of candle wax on heating
Option (d) is the answer. Wax changes its physical state on heating but not the properties so it does not involve any chemical change but involves physical change
- ChemistryClass 10ICSE
One of the following does not happen during a chemical reaction This is : (a) Breaking of old chemical bonds and formation of new chemical bonds (b) Formation of new substances with entirely different properties (c) Atoms of one element change into those of another element to form new products A rearrangement of atoms takes place to form new products
Option (c) is the answer. Atoms of one element does not change into another element to form products but the bonds between these atom will break and form products and atoms are rearrange also
- ChemistryClass 10ICSE
What do you understand by exothermic and endothermic reactions? (b) Give one example of an exothermic reaction and one of an endothermic reaction. (c) Which of the following are endothermic reactions and which are exothermic reactions? (i) Burning of natural gas (ii) Photosynthesis (iii) Electrolysis of water Solution: (iv) Respiration (v) Decomposition of calcium carbonate
Exothermic reaction is a reaction takes place when energy is released from the system into the surroundings Endothermic reaction is a reaction takes place when energy is absorbed from surroundings in the form of heat The thermal decomposition of Limestone CaCO3(s)→CaO (s)+CO2(g) This is an example for endothermic reaction Burning of fuel is an example for exothermic reaction C8H18(l)+25O2(g)→16CO2(g)+18H2O (g)+heat <li
- ChemistryClass 10ICSE
State the various characteristics of chemical reactions. (b) State one characteristics each of the chemical reaction which takes place when: (i) Dilute hydrochloric acid is added to sodium carbonate (ii) Lemon juice is added gradually to potassium permanganate solution (iii) Dilute sulphuric acid is added to barium chloride solution (iv) Quicklime is treated with water Wax is burned in the form of a candle
A chemical reaction is a reaction that takes place to form new substance by reacting with It is characterised by Evolution of a gas, Change in colour, Formation of a precipitate, Change in temperature, Change in state. (i) Evolution of Carbon dioxide gas Change in colour from purple to colourless Formation of a white precipitate of Barium sulphate Change in temperature, an exothermic reaction Change in state from solid to liquid and gas
- ChemistryClass 10ICSE
What is meant by a chemical reaction? Explain with the help of an example. (b) Give one example each of a chemical reaction characterised by: (i) Evolution of a gas (ii) Change in colour (iii) Formation of a precipitate (iv) Change in temperature Change in state.
A chemical reaction results in new substances by undergoing certain reactions and There will be reactants on the left hand side and products on the right hand side. An example of combustion is methane + oxygen forms carbon dioxide and water. This can be written as a balanced symbol equation: CH4 + 2O2 →CO2 + 2H2O (i) Evolution of gas Reaction of Zinc and Hydrochloric acid Zn + 2HCl → ZnCl2 + H2(g)
- ChemistryClass 10ICSE
• When potassium nitrate is heated, it decomposes into potassium nitrite and oxygen. Write a balanced equation for this reaction and add the state symbols of the reactants and products.
2KNO3 (s)→ 2KNO2 (s) + O2 (g)
- ChemistryClass 10ICSE
Translate the following statement into chemical equation and then balance it: ‘Barium chloride solution reacts with aluminium sulphate solution to form a precipitate of barium sulphate and aluminium chloride solution’.
3BaCl2 (aq) + Al2(SO4)3 (aq) → 3BaSO4 (s) + 2AlCl3 (aq)
- ChemistryClass 10ICSE
Write a balanced chemical equation for the process of photosynthesis giving the physical states of all the substances involved and the conditions of the reaction.
6CO2 (g) + 6H2O (l) → C6H12O6 (aq.) + 6O2 (g) in the presence of sunlight
- ChemistryClass 10ICSE
Ammonia reacts with oxygen to form nitrogen and water. Write a balanced chemical equation for this reaction. Add the state symbols for all the reactants and products.
4NH3 (g) + 3O2 (g) → 2N2 (g) + 6H2O (l)
- ChemistryClass 10ICSE
(a) Substitute formulae for names and balance the following equations: Calcium carbonate reacts with hydrochloric acid to produce calcium chloride, water and carbon dioxide gas. (b) Write balanced chemical equation with state symbols for the following reaction: Sodium hydroxide solution reacts with hydrochloric acid solution to produce sodium chloride solution and water.
(a) CaCO3 + 2HCl → CaCl2 + H2O + CO2 (b) NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)
- ChemistryClass 10ICSE
(a) Potassium chlorate (KClO3) on heating forms potassium chloride and oxygen. Write a balanced equation for this reaction and indicate the evolution of gas. (b) Rewrite the following information in the form of a balanced chemical equation: Magnesium burns in carbon dioxide to form magnesium oxide and carbon.
(a) 2KClO3 (s) → 2KCl (s) + 3O2 (g) (b) 2Mg + CO2 → 2MgO + C
- ChemistryClass 10ICSE
Carbon monoxide reacts with hydrogen under certain conditions to form methanol (CH3OH). Write a balanced chemical equation for this reaction indicating the physical states of reactants and product as well as the conditions under which this reaction takes place.
CO(g) + 2H2(g) → CH3OH Pressure: 300atm Temperature: 300℃ Catalyst: zinc oxide and chromium oxide
- ChemistryClass 10ICSE
Write the balanced chemical equations for the following reactions, and add the state symbols: (a) Magnesium carbonate reacts with hydrochloric acid to produce magnesium chloride, carbon dioxide and water. Sodium hydroxide reacts with sulphuric acid to produce sodium sulphate and water.
MgCO3 (s) + 2HCl (aq) →MgCl2 (aq) + CO2 (g) + H2O (l) 2NaOH (aq) + H2SO4 (aq) →Na2SO4 (aq) + 2H2O (l)
- ChemistryClass 10ICSE
Aluminium hydroxide reacts with sulphuric acid to form aluminium sulphate and water. Write a balanced equation for this reaction. (b) Balance the following chemical equation: MnO2 + HCl → MnCl2 + Cl2 + H2O
(a) 2Al(OH)3 + 3H2SO4 → Al2(SO4)3 + 6H2O (b) MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O
- ChemistryClass 10ICSE
Write any two observations in an activity which may suggest that a chemical reaction has taken place. Give an example in support of your answer
Change in temperature When calcium oxide reacts vigorously with water to produce calcium hydroxide a large amount of heat is evolved and thus temperature of the system increases hence it confirms that a chemical reaction has been taken place. Gas evolution When calcium carbonate is heated it decomposes into calcium oxide and carbon dioxide. Here carbon dioxide is a gas and thus confirms a chemical reaction
- ChemistryClass 10ICSE
(a) Explain, with example, how the physical states of the reactants and products can be shown in a chemical equation. (a) Balance the following equation and add state symbols: Zn + HCl → ZnCl2 + H2 (b) Convey the following information in the form of a balanced chemical equation: "An aqueous solution of ferrous sulphate reacts with an aqueous solution of sodium hydroxide to form a precipitate of ferrous hydroxide and sodium sulphate remains in solution."
The physical state of the reactants and products in a chemical reaction can be shown by using the letters in the round brackets if it is solid then (s) liquid (l) gas (g) and aqueous (aq) Example: Ca(OH)2 (aq) + CO2 (g) → CaCO3 (s) + H2O (l) Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g) FeSO4(aq) + 2NaOH (aq) → Fe(OH)2 (s) + Na2SO4 (aq)
- ChemistryClass 10ICSE
What is a balanced chemical equation? Why should chemical equations be balanced? b) Aluminium burns in chlorine to form aluminium chloride (AlCl3). Write a balanced chemical equation for this reaction. c) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. Write a balanced chemical equation for this reaction.
A chemical equation can be written by balancing total number of atoms of each element in reactants and A chemical equation should be balanced so that it can follow Law of conservation of mass. 2Al + 3Cl2 → 2AlCl3 2K + 2H2O → 2KOH + H2