Check the correct answer. Which of the following bears a diatomic molecule?
i. Helium
ii. Nitrogen
iii. Sulphur
iv. Phosphorus
Which of the following is a chemical change?
i. Melting of ice
ii. Breaking a stone
iii. Burning coal
iv. Boiling of water
Which of the following is an exothermic reaction?
i. [tex]$CaO + H _2 O \longrightarrow Ca ( OH )_2$[/tex]
ii. [tex]$2 KClO _3 \longrightarrow 2 KCl +3 O _2$[/tex]
iii. [tex]$N _2+ O _2 \longrightarrow 2 NO$[/tex]
When a piece of granulated zinc was added into the test tube containing dilute HCl, a gas was produced. What gas is it?
i. Carbon dioxide
ii. Ammonia
iii. Oxygen
iv. Hydrogen
What does the symbol ([tex]$\rightleftharpoons$[/tex]) represent?
i. Reactant
ii. Product
iii. Endothermic reaction
iv. Reversible reaction
What gas will be produced if [tex]$KClO _3$[/tex] is heated?
i. Hydrogen
ii. Oxygen
iii. Chlorine
iv. Potassium
If limestone is heated, what will be the products?
i. [tex]$Ca ( OH )_2+ O _2$[/tex]
ii. [tex]$CaO + CO _2$[/tex]
iii. [tex]$CaO + O _2$[/tex]
iv. [tex]$KCl + O _2$[/tex]
Answer (2)
The answers to the questions are: ii (Nitrogen), iii (Burning coal), i ( C a O + H 2 O → C a ( O H ) 2 ), iv (Hydrogen), iv (Reversible reaction), ii (Oxygen), and ii ( C a O + C O 2 ).
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Here's a summary of the answers:
Nitrogen bears a diatomic molecule.
Burning coal is a chemical change.
C a O + H 2 O ⟶ C a ( O H ) 2 is an exothermic reaction.
Hydrogen gas is produced when zinc reacts with dilute HCl.
The symbol ⇌ represents a reversible reaction.
Oxygen gas is produced when K Cl O 3 is heated.
C a O + C O 2 are the products when limestone is heated.
Explanation
Problem Analysis Let's analyze each question step by step:
Question a a. Diatomic molecules are molecules composed of only two atoms of the same or different chemical elements. Among the options, Nitrogen ( N 2 ) exists as a diatomic molecule. So the answer is ii.
Question b b. A chemical change involves the breaking and forming of chemical bonds, resulting in a new substance. Burning coal is a chemical change because it involves the oxidation of carbon to form carbon dioxide. So the answer is iii.
Question c c. An exothermic reaction releases heat. The reaction C a O + H 2 O ⟶ C a ( O H ) 2 (formation of calcium hydroxide) releases heat. So the answer is i.
Question d d. Zinc reacts with dilute hydrochloric acid (HCl) to produce zinc chloride ( Z n C l 2 ) and hydrogen gas ( H 2 ). So the answer is iv.
Question e e. The symbol ⇌ represents a reversible reaction, indicating that the reaction can proceed in both forward and reverse directions. So the answer is iv.
Question f f. When potassium chlorate ( K Cl O 3 ) is heated, it decomposes to produce potassium chloride ( K Cl ) and oxygen gas ( O 2 ). So the answer is ii.
Question g g. When limestone ( C a C O 3 ) is heated, it decomposes to produce calcium oxide ( C a O ) and carbon dioxide ( C O 2 ). So the answer is ii.
Examples
Understanding chemical reactions and their products is crucial in various real-life applications. For instance, knowing the products of burning fuels helps in designing efficient combustion engines. Identifying exothermic reactions aids in developing heating systems, while understanding reversible reactions is essential in chemical manufacturing processes. The ability to predict the outcomes of chemical processes allows us to control and utilize them effectively in numerous industries and daily life scenarios.
