Fill in the blanks
1. The rate of a chemical reaction is defined as the change in __________ per unit time.
2. Precipitation of silver chloride is an example of an __________ reaction.
3. The negative sign in the rate expression of reactants indicates a decrease in __________.
4. Instantaneous rate is obtained when the time interval Δt approaches __________.
5. The slope of the tangent drawn on a concentration-time graph gives the __________ rate of reaction.
6. In gaseous reactions, rate may also be expressed in terms of change in __________ pressure.
7. For the reaction 2HI → H₂ + I₂, the rate of disappearance of HI is __________ times the rate of formation of H₂.
8. Average rate of reaction depends on change in concentration and the time __________.
9. In the reaction Hg + Cl₂ → HgCl₂, the rates of disappearance and appearance are __________ because all stoichiometric coefficients are one.
10. The unit of reaction rate when concentration is expressed in mol L⁻¹ and time in seconds is __________.
Short QAs
1. What is meant by rate of a chemical reaction?
2. Why is rusting of iron considered a slow reaction?
3. Why is precipitation of silver chloride called an instantaneous reaction?
4. What is average rate of reaction?
5. What is instantaneous rate of reaction?
6. Why is a negative sign used in the rate expression for reactants?
7. What are the units of reaction rate?
8. How is instantaneous rate determined graphically?
9. Why are stoichiometric coefficients used in rate expressions?
10. How can the rate of a gaseous reaction be expressed?
MCQs
1. Rate of reaction is the change in:
A) Temperature B) Concentration per unit time C) Pressure only D) Volume only
2. Which is a very fast reaction?
A) Rusting of iron B) Hydrolysis of starch C) Precipitation of AgCl D) Inversion of cane sugar
3. Rusting of iron is a:
A) Fast reaction B) Slow reaction C) Instantaneous reaction D) Explosive reaction
4. Inversion of cane sugar is a:
A) Slow reaction B) Moderate reaction C) Instant reaction D) Very fast reaction
5. Average rate of disappearance of reactant is:
A) Δ[R]/Δt B) –Δ[R]/Δt C) d[R]/dt D) Δt/Δ[R]
6. Negative sign in rate of reactant is used because:
A) Time decreases B) Product decreases C) Reactant concentration decreases D) Pressure increases
7. Rate of appearance of product is:
A) Positive B) Negative C) Zero D) Infinite
8. Unit of reaction rate is:
A) mol L⁻¹ s⁻¹ B) mol² s⁻¹ C) L mol⁻¹ D) s mol⁻¹
9. For gaseous reactions, rate may be expressed in:
A) kg s⁻¹ B) atm s⁻¹ C) m s⁻¹ D) joule s⁻¹
10. Instantaneous rate is rate at:
A) Long interval B) Particular instant C) Equilibrium only D) Initial stage only
11. Instantaneous rate is obtained when:
A) Δt → ∞ B) Δt → 0 C) t = 1 D) Δ[R] = 0
12. Instantaneous rate expression represents:
A) Average rate B) Instantaneous rate C) Equilibrium constant D) Order of reaction
13. Graphically instantaneous rate is given by:
A) Area under curve B) Slope of tangent C) Intercept D) Curve length
14. Average rate is:
A) Constant over interval chosen B) Always increasing C) Always decreasing D) Infinite
15. For reaction R → P, rate of disappearance of R equals:
A) Twice product rate B) Half product rate C) Rate of appearance of P D) Zero
16. For 2HI → H₂ + I₂, rate expression contains factor:
A) 1/2 for HI B) 2 for H₂ C) 3 for I₂ D) 1/4 for HI
17. In rate expression stoichiometric coefficients are used to:
A) Change units B) Make all rates equal C) Increase speed D) Stop reaction
18. For aA + bB → cC, rate is divided by:
A) Molecular masses B) Stoichiometric coefficients C) Atomic numbers D) Temperature
19. In reaction Hg + Cl₂ → HgCl₂, rates of disappearance and appearance are:
A) Different B) Equal C) Zero D) Unrelated
20. For gaseous reactions concentration is proportional to:
A) Volume B) Pressure C) Density D) Temperature only
21. Hydrolysis of starch is:
A) Very fast B) Moderate C) Instantaneous D) Explosive
22. Which is not a unit of reaction rate?
A) mol L⁻¹ s⁻¹ B) atm s⁻¹ C) mol L⁻¹ D) concentration time⁻¹
23. Rate of reaction can be expressed in terms of:
A) Reactant concentration B) Product concentration C) Both A and B D) Catalyst only
24. Average rate depends on:
A) Change in concentration B) Time interval C) Both A and B D) Pressure only
25. Instantaneous rate is more useful because it gives rate:
A) Over long interval B) At a specific moment C) At equilibrium only D) For products only
26. Rate of disappearance of reactants is generally:
A) Positive B) Negative in expression C) Zero D) Infinite
27. Reaction rate generally:
A) Always increases with time B) Usually decreases with time C) Remains infinite D) Remains zero
28. Slope of concentration-time graph gives:
A) Equilibrium constant B) Reaction rate C) Activation energy D) Order
29. If reactant concentration decreases rapidly, reaction is:
A) Slow B) Fast C) Stopped D) Reversible only
30. Chemical kinetics mainly studies:
A) Rate of reaction B) Reaction mechanism C) Factors affecting rate D) All of these

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