List of top Chemistry Questions asked in ICSE Class X board

State whether the following statements are True or False. 

(a) Organic compounds having different molecular formula, but same structural formula are called isomers. 
(b) A salt is a compound formed by partial or complete replacement of the hydrogen ion of an acid by a metal or electropositive ion. 
 

Anil is a laboratory assistant in a college. He prepared nitric acid but stored it in a transparent container exposed to sunlight. After a few days, brown fumes were observed in the container and the acid turned slightly yellowish in colour. 

(a) What was the error made by Anil while storing the acid? 
(b) Why were brown fumes observed in the container? 
(c) How can the yellowish tinge in the acid be removed? 
 

(Zn + 4HNO_3 Zn(NO_3)_2 + 2H_2O + 2NO_2) 
32.5 g of zinc reacts with concentrated nitric acid as given in the above equation. 

(a) How many moles of zinc was required in the reaction? 
(b) Find the mass of nitric acid needed to react with 32.5 g of zinc. 
(c) Find the volume of nitrogen dioxide liberated in (b). 
(Atomic weight: H = 1, N = 14, O = 16, Zn = 65) 
 

Bauxite is the principal ore used in the commercial extraction of aluminium. The Bayer’s process is used to refine bauxite into pure alumina, with caustic soda playing a crucial role in the initial stage of the process. Based on this, answer the following questions: 

(a) Explain the reason behind the addition of caustic soda during the Bayer’s process. 
(b) Write a balanced chemical equation representing the reaction between bauxite and caustic soda during the Bayer’s process. 
 

Give one relevant observation for the following: 

(a) Sodium hydroxide is added dropwise to Calcium nitrate solution. 
(b) Dilute Hydrochloric acid is added to Iron (II) sulphide. 
(c) An amphoteric metal is added to hot concentrated alkali. 
 

Study the reaction scheme shown below and identify the reactants A, B and C. 

 

5.6 litres of gas Z weighs 32 g at STP. What is the molecular weight and vapour density of Z?
Name the following:
(a) The most electronegative element of Period 2
(b) The largest atom of Period 3

K, L and M are beakers containing three different solutions: [Beaker K: Aqueous acetic acid, Beaker L: Sodium chloride solution, Beaker M: Distilled water]. Name the beaker which: 
(a) contains only ions. 
(b) contains only molecules. 
(c) has pH less than 7. 

 

Carbon reacts with an acid to form carbon dioxide, water and nitrogen dioxide.
(a) Name the acid used in the reaction.
(b) Write a balanced chemical equation for the reaction that occurs.
Given below are a few elements: Li, K, Cs, F.
Identify the element which:
(a) has the least atomic radius.
(b) has two valence electrons.
(c) is the most electropositive.
During the manufacture of sulphuric acid, a chemist collected the gas formed after catalytic oxidation of sulphur dioxide.
(a) Name the gas collected.
(b) Which acid is formed when the gas collected by the chemist is dissolved directly in water?
(c) Why should we not dissolve this gas directly in water?
Elements P, Q, and R are in the same period of the modern periodic table.
• P readily loses its one valence electron to form a stable ion.
• Q shares its electrons in bonding but does not form ions easily.
• R has high electronegativity.
Equal volumes of ammonia gas and chlorine gas are kept in two different containers under the same conditions of temperature and pressure. Find the number of molecules contained in chlorine gas when the mass of ammonia is 34 g. (Atomic weight: Cl = 35.5, H = 1, N = 14)
Alex was given a solution of an unknown salt Y for analysis. He performed the following tests and recorded his observations:
• To a part of the solution Y, he added silver nitrate solution and obtained a white precipitate which was soluble in ammonium hydroxide solution.
• To the remaining solution he added a few drops of sodium hydroxide solution and obtained a pale blue precipitate.
Based on the observations made by Alex, identify:
(a) the anion and
(b) the cation present in salt Y.
Study the reaction given below and answer the questions that follow:
NaNO₃ + H₂SO₄ → NaHSO₄ + HNO₃ (below 200°C)
(a) Give one reason for maintaining the temperature below 200°C.
(b) Why is concentrated Sulphuric acid used in the above reaction?
What volume of carbon dioxide is produced at STP when 5 litres of propane is burnt completely according to the equation given below?
[ C_3H_8 + 5O_2 3CO_2 + 4H_2O ]
The compound that has the highest melting point amongst the following is:
With respect to the electrolysis of copper (II) sulphate solution using copper electrodes, which statement is correct?