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Read the following passage and answer the questions that follow:
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The rate of reaction is concerned with decrease in the concentration of reactants or increase in the concentration of products per unit of time. It can be expressed as instantaneous rate at a particular instant of time and average rate over a large interval of time. A number of factors such as temperature, concentration of reactants, catalyst affect the rate of reaction. Mathematical representation of rate of a reaction is given by rate law: Rate = k[A]x [B]y x and y indicate how sensitive the rate is to change in concentration of A and B. Sum of x + y gives the overall order of a reaction. |
- What is the effect of temperature on the rate constant of a reason? [1]
- For a reaction \[\ce{A + B → Product}\], the rate law is given by, Rate = k[A]2 [B]1/2. What is the order of the reaction? [1]
- How order and molecularity are different for complex reactions? [1]
- A first-order reaction has a rate constant 2 × 10–3 s–1. How long will 6 g of this reactant take to reduce to 2 g? [2]
OR
The half-life for radioactive decay of 14C is 6930 years. An archaeological artifact containing wood had only 75% of the 14C found in a living tree. Find the age of the sample.
[log 4 = 0.6021, log 3 = 0.4771, log 2 = 0.3010, log 10 = 1] [2]
Concept: Factors Influencing Rate of a Reaction
The following experimental rate data were obtained for a reaction carried out at 25°C:
\[\ce{A_{(g)} + B_{(g)} -> C_{(g)} + A_{(g)}}\]
| Initial [A(g)]/mol dm−3 | Initial [B(g)]/mol dm−3 | Initial rate/mol dm−3s−1 |
| 3.0 × 10−2 | 2.0 × 10−2 | 1.89 × 10−4 |
| 3.0 × 10−2 | 4.0 × 10−2 | 1.89 × 10−4 |
| 6.0 × 10−2 | 4.0 × 10−2 | 7.56 × 10−4 |
What are the orders with respect to A(g) and B(g)?
Concept: Zero Order Reactions
What happens to the rate constant k and activation energy Ea as the temperature of a chemical reaction is increased? Justify.
Concept: Temperature Dependence of the Rate of a Reaction
Account for the following:
Cr2+ is a strong reducing agent.
Concept: Physical Properties of the Transition Elements (d-block)
When chromite ore FeCr2O4 is fused with NaOH in presence of air, a yellow-coloured compound (A) is obtained, which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCl forms an orange coloured crystalline compound (C).
(i) Write the formulae of the compounds (A), (B) and C.
(ii) Write one use of compound (C).
Concept: Important Compounds of Transition Elements
Complete the following chemical equation
8MnO4- + 3S2O32- + H2O →
Concept: Important Compounds of Transition Elements
What are the transition elements? Write two characteristics of the transition elements.
Concept: Physical Properties of the Transition Elements (d-block)
How would you account for the following:
Actinoid contraction is greater than lanthanoid contraction.
Concept: F-block Elements >> The Actinoids
How would you account for the following : Transition metals form coloured compounds
Concept: Physical Properties of the Transition Elements (d-block)
Complete the following equation :
`2MnO_4^(-)+6H^++5NO_2^(-)rarr`
Concept: Important Compounds of Transition Elements
Account for the following:
Cu+ ion is unstable in aqueous solution.
Concept: Physical Properties of the Transition Elements (d-block)
Complete the following equations:Cr2O72- + 2OH- →
Concept: Important Compounds of Transition Elements
Complete the following equations : MnO4- + 4H+ + 3e- →
Concept: Important Compounds of Transition Elements
With reference to structural variability and chemical reactivity, write the differences between lanthanoids and actinoids
Concept: F-block Elements >> The Actinoids
Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.
Concept: F-block Elements >> The Lanthanoids
Out of Mn3+ and Cr3+, which is more paramagnetic and why ?
(Atomic nos. : Mn = 25, Cr = 24)
Concept: Physical Properties of the Transition Elements (d-block)
Complete the following chemical equation
Cr2O72- + 3Sn2+ + 14H+ →
Concept: Important Compounds of Transition Elements
Explain why Cu+ ion is not stable in aqueous solutions?
Concept: Physical Properties of the Transition Elements (d-block)
How is the variability in oxidation states of transition metals different from that of the non-transition metals? Illustrate with examples.
Concept: Physical Properties of the Transition Elements (d-block)
Indicate the steps in the preparation of KMnO4 from pyrolusite ore.
Concept: Important Compounds of Transition Elements
