Q11. What is the role of a catalyst in a chemical reaction?
Ans: A catalyst speeds up a chemical reaction without being consumed in it.
Q12. What happens when magnesium ribbon is burnt in air?
Ans: It burns with a bright white flame to form magnesium oxide.
Equation: 2Mg + O2 → 2MgO
Q13. Define exothermic reaction with example.
Ans: A reaction in which heat is released.
Example: C + O2 → CO2 + heat
Q14. What is a redox reaction?
Ans: A reaction in which oxidation and reduction occur simultaneously.
Q15. What is the color change in the reaction of copper with silver nitrate?
Ans: The blue solution fades and a grey deposit of silver forms.
Q16. What is neutralization reaction?
Ans: A reaction between acid and base to form salt and water.
Example: HCl + NaOH → NaCl + H2O
Q17. Give an example of a photochemical reaction.
Ans: Decomposition of silver chloride in sunlight:
2AgCl → 2Ag + Cl2
Q18. Name a reaction used in black and white photography.
Ans: Decomposition of silver bromide:
Ans: A catalyst speeds up a chemical reaction without being consumed in it.
Q12. What happens when magnesium ribbon is burnt in air?
Ans: It burns with a bright white flame to form magnesium oxide.
Equation: 2Mg + O2 → 2MgO
Q13. Define exothermic reaction with example.
Ans: A reaction in which heat is released.
Example: C + O2 → CO2 + heat
Q14. What is a redox reaction?
Ans: A reaction in which oxidation and reduction occur simultaneously.
Q15. What is the color change in the reaction of copper with silver nitrate?
Ans: The blue solution fades and a grey deposit of silver forms.
Q16. What is neutralization reaction?
Ans: A reaction between acid and base to form salt and water.
Example: HCl + NaOH → NaCl + H2O
Q17. Give an example of a photochemical reaction.
Ans: Decomposition of silver chloride in sunlight:
2AgCl → 2Ag + Cl2
Q18. Name a reaction used in black and white photography.
Ans: Decomposition of silver bromide:
