Q25 of 47 Page 1

a. Define order of reaction. How does order of a reaction differ from molecularity for a complex reaction?

b. A first order reaction is 50% complete in 25 minutes. Calculate the time for 80% completion of the reaction.


OR


a. The decomposition of a hydrocarbon has value of rate constant as 2.5 × 104 s-1 at 27oC. At what temperature would rate constant be7.5 × 104 s-1 if energy of activation is 19.147 × 103 J mol-1?


b. Write a condition under which a bimolecular reaction is kinetically first order. Give an example of such a reaction.
(Given: log 2 = 0.3010, log 3 = 0.4771, log 5 = 0.6990)


a. Order of a reaction: It is the sum of the power to which the concentration terms are raised in the rate law equation. It can be 0,1 or 2


Molecularity is the minimum no. of molecules taking part in a chemical reaction.
Order of reaction is applicable for complex reaction but molecularity has no meaning for the complex reaction.


b. Given: T1/2= 25 minutes


For 1st order reaction, T1/2=


k = = 0.0277 min-1


now, as 80% reaction is complete, so amount left [R] =100-80 = 20


T =


T =


T= 58.113 minutes


OR


a. k1= 2.5 × 104 s-1 T1= 270C = 300K


k2= 7.5 × 104 s-1 T2= ?


Ea= 19.147 × 103 J/mol


We know that







b. A bimolecular reaction is kinetically first order when one of the reactants is in excess.


For Example:


CH3COOCH3 + H2O (excess) → CH3COOH + CH3OH


More from this chapter

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23

a. Give one chemical test as an evidence to show that [Co(NH3)5CI]SO4 and [Co(NH3)5(SO4)]CI are ionisation isomers.

b. [NiCL4]2- is paramagnetic while [Ni(CO)4] is diamagnetic though both are tetrahedral. Why? (Atomic no. of Ni = 28)


c. Write the electronic configuration of Fe(III) on the basis of crystal field theory when it forms an octahedral complex in the presence of


i. strong field ligand, and


ii. weak field ligand.
(Atomic no. of Fe = 26)


 24

Define the following terms with a suitable example of each :

a. Anomers


b. Essential amino acids


c. Denaturation of protein


 26

a. Predict the main product of the following reactions :

i.


ii.


iii.


b. Give a simple chemical test to distinguish between


c. Why is alpha (α) hydrogen of carbonyl compounds acidic in nature?


OR


a. Write the main product formed when propanal reacts with the following reagents :


i. 2 moles of CH3OH in presence of dry HCl


ii. Dilute NaOH


iii. H2N – NH2 followed by heating with KOH in ethylene glycol


b. Arrange the following compounds in increasing order of their property as indicated :


i. F - CH2COOH, O2N - CH2COOH, CH3COOH, HCOOH - acid character


ii. Acetone, Acetaldehyde, Benzaldehyde, Acetophenone - reactivity towards addition of HCN


 27

a. Account for the following :

i. Manganese shows maximum number of oxidation states in 3d series.


ii. Eo value for Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.


iii. Ti4+ is colourless whereas V4+ is coloured in an aqueous solution.


b. Write the chemical equations for the preparation of KMnO4 from MnO2. Why does purple colour of acidified permanganate solution decolourise when it oxidises Fe2+ to Fe3+?


OR


a. Write one difference between transition elements and p-block elements with reference to variability of oxidation states.


b. Why do transition metals exhibit higher enthalpies of atomization?


c. Name an element of lanthanoid series which is well known to shown +4 oxidation state. Is it a strong oxidising agent or reducing agent?


d. What is lanthanoid contraction? Write its one consequence.


e. Write the ionic equation showing the oxidation of Fe(II) salt by acidified dichromate solution.