Q26 of 26 Page 1

For the hydrolysis of methyl acetate in aqueous solution, the following results were obtained :

(a) Show that it follows pseudo first order reaction, as the concentration of water remains constant.


(b) Calculate the average rate of reaction between the time interval 10 to 20 seconds.


(Given: log 2 = 0.3010, log 4 = 0.6021).


OR


(a) For a reaction A + B → P, the rate is given by Rate = k[A][B]2


(i) How is the rate of reaction affected if the concentration of B is doubled ?


(ii) What is the overall order of reaction if A is present in large excess ?


(b) A first order reaction takes 30 minutes for 50% completion. Calculate the time required for 90% completion of this reaction.


(a) [A]0 = 0.01 Mol/L

[A] = 0.05 Mol/L at time t = 10s.



k = 0.0693 s-1


t = 20 s



K = 0.0693 s-1, Thus its pseudo first order reaction.


(b) The average rate constant is




= 0.0025 mol L-1s-1


OR


(a) (i) Since the given reaction has order 2 with respect to reactant B, if the concentration of B is doubled in the given reaction, then the rate of reaction will become four times.


(ii) It the concentration of B is doubled i.e., [B]2 the overall reaction will be two, because if A is present in large excess, then the reaction will be independent of the concentration of A and will be dependent only on the concentration of B.


Order of reaction = 2.


(b) t1/2= 30 min


[R] = [R]0 – 90% of [R]0







t = 99.7 min.


More from this chapter

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22

Write the names and structures of the monomers of the following polymers:

(i) Terylene


(ii) Buna-S


(iii) Neoprene


 23

Seeing the growing cases of diabetes and depression among young children, Mr. Chopra, the principal of one reputed school organized a seminar in which he invited parents and principals. They all resolved this issue by strictly banning junk food in schools and introducing healthy snacks and drinks like soup, lassi, milk, etc. in school canteens. They also decided to make compulsory half an hour of daily physical activities for the students in the morning assembly. After six months, Mr. Chopra conducted the health survey in most of the schools and discovered a tremendous improvement in the health of the students.

After reading the above passage, answer the following questions:


(i) What are the values (at least two) displayed by Mr. Chopra ?


(ii) As a student, how can you spread awareness about this issue?


(iii) Why should antidepressant drugs not be taken without consulting a doctor?


(iv) Give two examples of artificial sweeteners.


 24

(a) Account for the following :

(i) Acidic character increases from HF to HI.


(ii) There is a large difference between the melting and boiling points of oxygen and sulphur.


(iii) Nitrogen does not form pentahalide.


(b) Draw the structures of the following:


(i) ClF3


(ii) XeF4


OR


(i) Which allotrope of phosphorus is reactive and why ?


(ii) How are the supersonic jet aeroplanes responsible for the depletion of ozone layer ?


(iii) F2 has lower bond dissociation enthalpy than Cl2. Why ?


(iv) Which noble gas is used in filling balloons for meteorological observations ?


(v) Complete the following equation :



 25

An aromatic compound ‘A’ of molecular formula C7H6O2 undergoes a series of reactions as shown below. Write the structures of A, B, C, D and E in the following reactions :


OR


(a) Write the structure of main products when benzene diazonium chloride reacts with the following reagents :


(i) H3PO2 + H2O


(ii) CuCN/KCN


(iii) H2O


(b) Arrange the following in the increasing order of their basic character in an aqueous solution:


C2H5NH2, (C2H5)2NH, (C2H5)3N


(c) Give a simple chemical test to distinguish between the following pair of compounds:


C6H5 – NH2 and C6H5 – NH – CH3