NET, IAS, State-SET (KSET, WBSET, MPSET, etc.), GATE, CUET, Olympiads etc.: Chemistry MCQs (Practice_Test 8 of 31)
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- Consider the following reaction in aqueous solution, 5Br- (aq) + BrO3- (aq) + 6H + (aq) ⇾ 3Br2 (aq) + 3H2O (l) If the rate of appearance of Br2 at a particular moment during the reaction is 0.025 M s − 1, what is the rate of disappearance (in M s − 1) of Br-at that moment?
- Consider the following reaction at 25oC (CH3) , 3COH (l) + HCl (aq) ⇾ (CH3) 3CCl (l) + H2O (l) The experimentally determined rate law for this reaction indicates that the reaction is first-order in (CH3) 3COH and that the reaction is first-order overall. Which of the following would produce an increase in the rate of this reaction?
- increasing the concentration of (CH3) 3COH
- increasing the concentration of HCl
- decreasing the concentration of HCl
- decreasing the concentration of (CH3) 3CCl
- It is impossible to tell.
- A certain first-order reaction has a rate constant, k, equal to 2.1 × 10 − 5 s − 1 at 355 K. If the activation energy for this reaction is 135 kJ⟋mol, calculate the value of the rate constant (in s − 1) at 550 K.
- Which of the following influences the rate of a chemical reaction performed in solution?
- temperature
- activation energy
- presence of a catalyst
- concentrations of reactants
- All of the above influence the rate.
- Laughing gas, N2O, can be prepared (ha, ha!) from H2 and NO: H2 (g) + 2 NO (g) ⇾ N2O (g) + H2O (g) A study of initial concentration (ha, ha!) versus initial rate at a certain temperature yields the following data for this reaction (ha, ha!) : [H2] , M [NO] , Minitial rate, M s − 1 0.10000. 50002.560 × 10 − 6 0.20000. 30001.843 × 10 − 6 0.10000. 30009.216 × 10 − 7 0.20000. 60007.373 × 10 − 6 Which of the following is the correct rate law for this reaction (ha, ha!) ?
- Rate = k [H2] [NO] 2
- Rate = k [H2] [NO]
- Rate = k [NO] 2
- Rate = k [H2] 2
- Rate = k
- Iodine-131, a radioactive isotope of iodine, is used medicinally as a radiotracer for the diagnosis and treatment of illnesses associated with the thyroid gland. The half-life of iodine-131 is 7 × 105 seconds. If a patient is given 0.45 g of iodine-131, calculate how long it would take (in seconds) for 90.0% of the iodine-131 to decay. Recall: Radioactive decay is a first-order process.
- N⟋A
- N⟋A
- N⟋A
- N⟋A
- Consider a reaction which is first-order in A and first-order in B
- N⟋A
- N⟋A
- N⟋A
- N⟋A
- The complex ion, [Cr (NH3) 5Cl] 2 + , reacts with OH-ion in aqueous solution, [Cr (NH3) 5Cl] 2 + (aq) + OH- (aq) ⇾ [Cr (NH3) 5 (OH) ] 2 + (aq) + Cl- (aq) The following data were obtained for this reaction at 25oC [Cr (NH3) 5Cl] 2 + concentration (M)
- 01.00
- 60.657
- 120.432
- 180.284
- 240.186
- 300.122
- 360.0805
- The order of the reaction with respect to the [Cr (NH3) 5Cl] 2 + ion is:
- zero order
- first order
- second order
- third order
- fourth order
- A student determined the value of the rate constant, k, for a chemical reaction at several different temperatures. Which of the following graphs of the student՚s data would give a straight line?
- k versus T
- k versus (1⟋T)
- ln k versus (1⟋T)
- ln k versus T
- ln k versus Ea
- In the experiment, “How Can Spectrophotometric Methods Be Used to Determine the Order of a Chemical Reaction” it is necessary to remove invalid data points towards the end of the reaction. Which of the following statements best explains why this is necessary?
- The Spectronic 20 becomes unstable towards the end of the reaction.
- Towards the end of the reaction, the temperature of the solution is significantly different than the initial temperature of the solution.
- Towards the end of the reaction, the concentrations of the reactants are so high that it is difficult to measure them accurately.
- Towards the end of the reaction, the concentrations of the products are sufficiently high that the reverse reaction competes with the forward reaction.
- None of these.
- The next two questions are about this reaction: 2N2O5 (g) ⟺ 4NO2 (g) + O2 (g) The rate law for the above reaction is:
- rate = k [N2O5] 2
- rate = [N2O5] 2
- rate = k [N2O5] 2⟋ [NO2] 4 [O2] 1
- rate = k [N2O5] x
- rate = [N2O5] x
- The next two questions are about this reaction: 2N2O5 (g) ⟺ 4NO2 (g) + O2 (g) If the instantaneous rate of appearance of NO2 (g) is 0.0400 M⟋s at some moment in time, what is the rate of disappearance of N2O5 (g) in M⟋s?
- N⟋A
- N⟋A
- N⟋A
- N⟋A
- The rate laws for certain enzyme-activated reactions in your body have a specific rate constant k, with units of M⟋s. What is the overall order of these reactions?
- 0
- 1
- 2
- 3
- Cannot be determined.
- The next two questions are about this reaction: 2NO (g) + Cl2 (g) ⟺ 2NOCl (g) The rate law for the above reaction has been determined to be rate = k [NO] [Cl2] . What is the overall order of the reaction?
- 0
- 1
- 2
- 3
- Cannot be determined.
- The next two questions are about this reaction: 2NO (g) + Cl2 (g) ⟺ 2NOCl (g) A mechanism involving the following steps has been proposed for the above reaction:
- NO (g) + Cl2 (g) ⇾ NOCl2 (g)
- NOCl2 (g) + NO (g) ⇾ 2NOCl (g)
- N⟋A
- N⟋A
- N⟋A
- N⟋A