Physical Chemistry Questions

where do u find elements phases at STP?

systems in nature tend to undergo changes ____ increased enthropy

For what type of reactions is the solubility sheet needed?

2 The data in Table 2 were obtained in two experiments on the rate of the reaction between compounds C and D at a constant temperature.The rate equation for this reaction israte = k[C]2[D](b) Use the data from experiment 4 to calculate a value for the rate constant, k, at this temperature. Deduce the units of k.

2 (d) The rate equation for a reaction israte = k[E]Explain qualitatively why doubling the temperature has a much greater effect on the rate of the reaction than doubling the concentration of E.

(e) A slow reaction has a rate constant k = 6.51 × 10−3 mol−1 dm3 at 300 K.Use the equation ln k = ln A - Ea / RT to calculate a value, in kJ mol−1, for the activation energy of this reaction.The constant A = 2.57 × 1010 mol−1 dm3.The gas constant R = 8.31 J K−1 mol−1.

1 (c) State how the initial rate is obtained from a graph of the concentration of the product against time.

6 (a) In the presence of the catalyst rhodium, the reaction between NO and H2 occurs according to the following equation.2NO(g) + 2H2(g) N2(g) + 2H2O(g)The kinetics of the reaction were investigated and the rate equation was found to berate = k[NO]2[H2]The initial rate of reaction was 6.2 × 10-6 mol dm-3 s-1 when the initial concentration of NO was 2.9 × 10-2 mol dm-3 and the initial concentration of H2 was 2.3× 10-2 mol dm-3.(i) Calculate the value of the rate constant under these conditions and give its units.

4. (c) The reaction is zero order with respect to B.State the significance of this zero order for the mechanism of the reaction.

6 a (ii) Calculate the initial rate of reaction if the experiment is repeated under the same conditions but with the concentrations of NO and of H2 both doubled from their original values.

3 The rate equation for the hydrogenation of etheneC2H4(g) + H2(g) C2H6(g)is Rate = k[C2H4][H2]At a fixed temperature, the reaction mixture is compressed to triple the original pressure.What is the factor by which the rate of reaction changes?

4. Gases A and B react as shown in the following equation.2A(g) + B(g) -> C(g) + D(g)The initial rate of the reaction was measured in a series of experiments at a constant temperature. The following rate equation was determined.rate = k[A]2An incomplete table of data for the reaction between A and B is shown in the table.

(c) The compound (CH3)3CBr reacts with aqueous sodium hydroxide as shown in the folfollowing equation.(CH3)₃CBr + OH⁻ → (CH3)₃COH + Br⁻This reaction was found to be first order with respect to (CH3)3CBr but zero order with respect to hydroxide ions.The following two-step process was suggested.Step 1 (CH3)3CBr (CH3)3C+ + Br−Step 2 (CH3)3C+ + OH− (CH3)3COH(i) Deduce the rate-determining step in this two-step process.(1)(ii) Outline a mechanism for this step using a curly arrow.

5 (c) The rate of decomposition of hydrogen peroxide is increased by the addition of cobalt(II) ions.Outline the essential features of an additional experiment to show that the rate of decomposition is increased by the addition of cobalt(II) chloride. Use the same method and the same apparatus as in part (a).

6 (b) Using the rate equation and the overall equation, the following three-step mechanism for the reaction was suggested. X and Y are intermediate species.Step 1 NO + NO → XStep 2 X + H2 → YStep 3 Y + H2 → N2 + 2H2OSuggest which one of the three steps is the rate-determining step.Explain your answer.

5. An equation for the decomposition of hydrogen peroxide is2H2O2 -> 2H2O + O2(a) The rate of reaction can be determined by collecting the oxygen formed and measuring its volume at regular intervals.Draw a diagram to show the apparatus that you would use to collect and measure the volume of the oxygen formed.

1 (b) Suggest why initial rates of reaction are used to determine these orders rather than rates of reaction at other times during the experiments.

1. a) The initial rate of the reaction between gases D and E was measured in a series of experiments at a constant temperature. The results are shown in the table.(a) Deduce the order of reaction with respect to D and the order with respect to E.

What types of equations can be used to show redox reactions of metals and their ions?

(1) What does MnO4 get reduced to What does Fe 2+ get oxidised to