Chapter-wise most important science questions for Board Exams

The best way to escape the exam fear is “Practice“. Practice all the questions given below for chemistry will you solve all the questions that will appear in CBSE Board Exam of Science.

Chemical Reactions and Equations

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VERY SHORT QUESTIONS (1 Mark)

1. What changes do you observe in the iron nails and colour of copper sulphate solution, if iron nails are dipped in CuSO4 solution for 15 minutes ?
2. Identify the chemical change : Melting of ice or conversion of milk into curd.
3. Why is respiration considered an exothermic reaction ?
4. Why do copper vessel lose shine when exposed to air ?
5. Potato chips manufacturers fill the packet of chips with nitrogen gas. Why ?
6. Why we store silver chloride in dark coloured bottles ?
7. Write a chemical equation of double displacement reaction.
8. N2 + 3H2 → 2NH3 , name the type of reaction.
9. What happens when milk is left open at room temperature during summers ?
10. What happens when quick lime is added to water ?

SHORT TYPE QUESTIONS (2 Marks)

1. Define combination reaction. Give one example of combination reaction which is exothermic in nature.
2. What is decomposition reaction ? Explain with the help of an example.
3. Name and state the law which is kept in mind when we balance a chemical equation.
4. Give one example of each :
(a) Chemical reaction showing evolution of gas.
(b) Change in substance’s colour during a chemical reaction.
5. What is rancidity ? Write two ways by which it can be prevented.
6. What are two conditions which promotes corrosion ?
7. A small amount of ferrous sulphate is heated in hard glass tube.
(a) Write the chemical equation.
(b) What type of reaction is taking place.
8. What happens when Zn strip is dipped in CuSO4 solution ?

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SHORT TYPE QUESTIONS (3 Marks)

1. What is redox reaction ? Write down a chemical reaction representing it.

2. In electrolysis of water :
(a) Name the gas collected at cathode and anode.
(b) Why is volume of one gas collected at one electrode is double of another ?
(c) Why are few drops of dil. H2SO4 added to water ?

3. In the reaction
CuO (s) + H2 (g) → Cu(s) + H2O (g)
(a) Name the oxidized substance.
(b) Name the reduced substance.
(c) Name the oxidizing agent.

4. Give reasons :
(a) White silver chloride turns grey in sunlight.
(b) Brown coloured copper powder on heating in air turns into black coloured substance.

5. Compound ‘X’ decomposes to form compound ‘Y’ and CO2 gas. Compound Y is used in manufacturing of cement.
(a) Name the compounds ‘X’ and ‘Y’.
(b) Write the chemical equation for this reaction.

6. A metal salt MX when exposed to light splits upto to form metal M and gas X2. Metal M is used to make ornaments whereas gas X2 is used in making bleaching powder. The salt MX is used in black & white photography.
(a) Identify the metal M and gas X2
(b)Identify MX.
(c) Write down the chemical reaction when salt MX is exposed to sunlight.

7. A metal strip X is dipped in blue coloured salt solution YSO4. After some time a layer of metal ‘Y’ is formed on metal strip X. Metal X is used in galvanization whereas metal Y is used for making electric wires.
(a) What could be metal ‘X’ and ‘Y’ ?
(b) Name the metal salt YSO4.
(c) What type of chemical reaction takes place between X and YSO4? Write the balanced chemical equation.

LONG TYPE QUESTIONS (5 Marks)
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1. White wash was being done at Mukesh’s house. Mukesh saw that the painter added quick lime to drum having water. Mukesh touched outer surface of drum, it is unbelievably hot.
(a) Write the chemical equation for above reaction.
(b) What type of reaction is it ?
(c) What is utility of this reaction ?

2. What types of reactions are represented by following :
(a) CaCO3 → CaO + CO2
(b) 2Ca + O2 → 2CaO
(c) Pb + CuCl2 → PbCl2 + Cu
(d) 2FeSO4 → Fe2O3 + SO2 + SO3
(e) Na2 SO4 + BaCl2 → BaCl2 + 2NaCl

3. Balance the following equations :
(a) H2 + O2 → H2O
(b) MnO2 + HCl → MnCl2 + H2O + Cl2
(c) Pb(NO3) → PbO + NO2 + O2
(d) AgNO3 + NaCl → AgCl + NaNO3
(e) Ca(OH)2 + HNO3 → Ca(NO3)2 + H2O

4. Write down the balanced chemical equation for the following :
(a) Silver chloride is decomposed in presence of sunlight to give silver and chlorine gas.
(b) Calcium oxide reacts with water to give lime water.
(c) Sodium hydroxide reacts with hydrochloric acid to give sodium chloride and water.
(d) Die hydrochloric acid is added to copper oxide to give green coloured copper chloride and water.
(e) Solution of barium chloride and sodium sulphate in water reacts to give insoluble barium sulphate and solution of sodium chloride.

Acids, Bases and Salts

VERY SHORT QUESTIONS (1 Mark)

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1. Name the acid present in ant sting.
2. What happens when egg shell is added to nitric acid ?
3. Name a salt which does not contain water of crystallization.
4. Name two constituents of baking powder.
5. What is the pH of gastric juices released during digestion ?
6. Which solution is used to dissolve gold ?
7. How will you test a gas which is liberated when HCl acid reacts with an active metal ?
8. Why does flow of acid rain water into a river make the survival of aquatic life in the river difficult ?
9. When conc. acid is added to water, whether the process is exothermic or endothermic ?
10. Which by-product of chlor-alkali process is used for manufacturing bleaching powder ?

SHORT TYPE QUESTIONS (2 Marks)

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1. Why does bleaching powder smell strongly of chlorine and does not dissolve completely in water ?
2. Hold one moist and one dry strip of blue litmus paper over dry HCl acid gas. Which strip will turn red and why ?
3. What is Plaster of Paris ? How is it obtained from gypsum ?
4. What is the role of toothpastes in preventing cavities ?
5. Explain why sour substances are effective in cleaning copper vessels ?
6. A white powder is added while baking breads and cakes to make them soft and fluffy. What is the name of the powder ? What are its main ingredients ?
7. How washing soda is prepared from baking soda ?
8. Though the compounds such as glucose and alcohol have hydrogen atoms in their molecule, yet they are not categorized as acids. Why ?
9. What is the reaction called when an acid reacts with base to produce salt and water ? Give example also.
10. Why pickles and curd are not stored in copper and brass utensils ?

SHORT TYPE QUESTIONS (3 Marks)

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1. On passing excess CO2 through lime water, it first turns milky and then becomes colourless. Explain why ? Write chemical equations.
2. How are bases different from alkalis ? Are all bases alkalis ?
3. While constructing a house, a builder selects marble flooring and marble top for kitchen where vinegar and juices of lemon, tamarind etc. are more often used for cooking. Will you agree to this selection and why ?
4. Indicate with the help of a diagram the variation of pH with change in concentration of H+ (aq) and OH−(aq) ions.
5. Write the name and formulae of three hydrated salts.
6. What happens when calcium carbonate is made to react with hydrochloric acid ? Give the equation of reaction.
7. Why metallic oxides are called basic oxides and non-metallic oxides are called acidic oxides ?
8. What is pH scale ? What is pH value of salt formed by a
(a) weak acid and strong base ?
(b) strong acid and strong base ?

LONG ANSWER TYPE QUESTIONS (5 Marks)

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1. What is water of crystallization ? Write the common name and chemical formula of a commercially important compound which has ten water molecules. How is this compound obtained ? Write chemical equations also. List any two uses of this compound.
2. An element P does not react with dil. H2SO4. If forms an oxide PO which turns red litmus into blue. Will you call P as a metal or a non-metal ? Give reason.

Metals and Non – Metals

VERY SHORT QUESTIONS (1 Mark)

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1. Name one lustrous non-metal.
2. Name two metals that are soft and can be cut with a knife.
3. Number of electrons gained or lost by an element is called its…………….. .
4. What are minerals ?
5. What is the process of depositing zinc on iron called ?
6. Which metal do not react with water at all ?
7. Name the ion made by non-metals – cation/anion.
8. Bronze is an alloy made by the combination of……………..and…………….. .
9. Name two metals that are stored in kerosene oil.
10. Arrange copper, silver and aluminium in increasing order of reactivity.

SHORT ANSWER TYPE QUESTIONS (2 Marks)

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1. Give reasons :
(a) Why is pure gold not suitable for making ornaments ?
(b) Why calcium is found in the form of compound ?
(c) Why electrical wires are coated with PVC (Poly Vinyl Chloride) ?
(d) Why do we apply oil on iron tools kept in storage ?
(e) Why sodium is stored in kerosene oil ?

SHORT ANSWER TYPE QUESTIONS (3 Marks)

1. Why caesium and gallium melt in our palm ?
2. Why magnesium ribbon starts floating in hot water ?
3. What are ionic compounds ?
4. To obtain metal from their metal oxide, which chemical process is used ? Give the chemical equation as well.

LONG ANSWER TYPE QUESTIONS (5 Marks)

1. What is the difference between a mineral and an ore ?
2. Differentiate between roasting and calcinations process in metallurgy.
3. What is an alloy ? Name the alloy which has iron, nickel and chromium as its constituent. What is the chief use of this alloy ?
4. Explain any two ways to prevent rusting of iron.
5. Explain briefly electrolytic refining method.

Carbon and its Compounds

VERY SHORT ANSWER TYPE QUESTIONS (1 Mark)

1. How does carbon attain noble gas configuration ?
2. Draw electron dot structure of water molecule.
3. Write the name and formula of 2nd member of homologous series having general formula CnH2n.
4. Name the first member of ketones.
5. What is glacial acetic acid ?
6. Why carbon is tetravalent ?
7. An organic compound burns with blue clear flame. Is it saturated or unsaturated compound ?
8. Write the molecular formula of ethanol.
9. Which of the following will show addition reaction : C4H10, C2H6, C2H4,CH4, C3H8 ?
10. Name the gas evolved when ethanoic acid is added to sodium carbonate ?
11. Write balanced chemical equation of dehydration of ethanol by hot conc.H2SO4.
12. Name organic acid present in vinegar.
13. What is catenation ?
14. Why soap is not suitable for washing cloth when water is hard ?
15. How many covalent bonds are present in pentane (C5H12) ?
SHORT ANSWER TYPE QUESTIONS (2 Marks)
1. What are hydrocarbons ? Give examples.
2. Why does carbon atom forms a large number of compounds ?
3. Write down two characteristics of the compounds of an homologous series.
4. Covalent compounds generally don’t conduct electricity. Why ?
5. Write down structural formula of :
(a) Propanone (b) Hexanal
6. Why carbon is unique in nature ?
7. Which is better for health butter or vegetable oil ? Why ?
8. Complete the following reactions :
(a) CH4 + O2 → (b) CH4 + Cl2 → Sunlight
9. Identify the functional group in following :
(a) HCHO (b) CH3COOH
(c) CH3CH2OH (d) CH3COCH3
10. (a) Why is ethanol used in making of tincture iodine, cough syrup, tonic etc.
(b) What is the role of conc. H2SO4 in making ethane from ethanol ?

SHORT ANSWER TYPE QUESTIONS (3 Marks)

1. Differentiate between soap and detergents.
2. What is oxidizing agent ? Give two examples.
3. What is hydrogenation ? Write its industrial application.
4. What is homologous series ? Explain with the help of example.
5. Write IUPAC names of :
(a) HC ≡ CH (b) CH3CH2CH2OH (c) CH2CHO
6. What is structural isomerism ? Draw isomers of pentane (C5H12).
7. A boy sharpens a pencil at both the ends and connects them to the poles of the battery. Will the current flow through the circuit ?Give reason.
8. A neutral organic compound is warmed with some ethanoic acid and a little of conc. H2SO4 to form ester, vapours having sweet smell are evolved. Write the chemical equation and what type of functional group is present in this organic compound ?

LONG ANSWER TYPE QUESTIONS (5 Marks)

1. Explain the cleansing action of soap with the help of diagram.
2. When ethanoic acid reacts with sodium hydrogen carbonate, the salt ‘X’ is formed and gas ‘Y’ is evolved.
(a) Identify ‘X’ and ‘Y’.
(b) Write balanced chemical equation of above reaction.
(c) Describe a test to identify the gas ‘Y’ evolved.

Periodic Classification of Elements

VERY SHORT ANSWER TYPE QUESTIONS (1 Mark)

Short Notes and Board Exam Questions: Periodic Classification of Elements

1. Write down three elements that show Dobereiner’s triad.
2. Write down two drawbacks of Newland’s law of octaves.
3. What was the need for classification of elements ?
4. Which important property did Mendeleev used to classify the elements in his periodic table ?
5. What do you mean by valency ?
6. How many elements are known till date ?
7. State Modern Periodic law.
8. Name the elements and its valency having electronic configuration 2, 8, 3.
9. How many rows and columns are there in modern periodic table ?
10. Why properties of elements are different of same period ?

SHORT ANSWER TYPE QUESTIONS (2 Marks)

1. How does the tendency to lose electrons change in a group and why ?
2. Why He, Ne and Ar are called inert gases ?
3. Write two limitations of Mendeleev’s Periodic Table.
4. Why is the position assigning to hydrogen in the periodic table considered anomalous ?
5. What do you mean by metallic character of an element ? How does it vary as we go down a group ? Give reason for this variation.
6. Why metallic oxides are basic in nature whereas non-metallic oxides are acidic in nature ?
7. How does the atomic size vary as we go down a group and move left to right in a period ? Write the reason behind it.

SHORT ANSWER TYPE QUESTIONS (3 Marks)

1. Four elements P, Q, R and S have atomic number 12, 13, 14 and 15 respectively. Answer the following :
(a) What is the valency of Q ?
(b) Classify these elements as metals and non-metals.
(c) Which of these elements will form the most basic oxide ?
2. (a) How do we calculate the valency of an element from its electronic configuration ?
(b) How does the valency vary in a period ?
3. Study the variation in the atomic radii of elements given below and arrange them in increasing order :
Na         Li          Rb             Cs            K
186    152      246          262        231

(a) Name the element which has the smallest and the largest atomic size.
(b) How does the atomic size vary as we go down a group ?
4. What are metalloids ? Write two examples.

LONG ANSWER TYPE QUESTIONS (5 Marks)
1. Write down five major differences between Mendeleev’s periodic table and Modern periodic table.
2. Element A has atomic no. 16.
(a) Name of the element
(b) Physical state
(c) Compound with hydrogen
(d) Metal or non-metal
(e) Nature and formula with oxides

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