- Organic Chemistry
- Aldehydes and Ketones
- Alkyl Halides, Alcohols and ethers
- Amines and other nitrogen compounds
- Aromatic Chemistry
- Carbohydrates, Amino acids, protein, Vitamin and Fat
- Carboxylic acids and its derivatives
- Chemistry in daily life
- General Mechanism in organic compounds
- Hydrocarbons
- Nomenclature and isomerism
102 - Physical Chemistry Questions Answers
which of the following have maximum value of enthalpy of physisorption?
(a) H2
(b) N2
(c) H2O
(d) CH4
(d) CH4 based on the value of energy which is 6 Kcal/mole for 0.1 milimole/gram and is greatest among the given 4
volume of gases H2 , CH4 , CO2 , and NH3 absorbed by 1g of charcoal at 288K are in the order
H2 4.7 cc per gm
CH4 16.2 cc per gm
CO2 48 cc per gm
NH3 181 cc per gm
the radiation from a naturally ocuring radioactive substance as seen after deflection by a magnetic field in one direction are
(a) α rays
(b) β rays
(c) both (a) & (b)
(d) either α or β-rays
(d) because one will move opposite to the other
the amount of U-235 required per day to run a power house of capacity 50 MW (efficiency of nuclear reactor 75%. Assume energy liberated by fission of 1 U-235 atom is 200 Mev) is
(a) 15.8gm
(b) 28.1gm
(c)21.1gm
(d) none of these
let x gm is required
then according to the given condition
(x/235)*6.023*1023*200*106*1.6*10-19 = 50*106*86400
solve
there are two radio nuclei A and B. A is α-emitter and B is a β-emitter, their decay constant are in the ratio 1:2. what should be the no. of atoms of A&B at time t=0, so that probability of getting α and β-particles are same at time t=0
(a) 2:1
(b) 1;2
(c) 1:4
(d) 4:1
its (b)
decay constant ratio = 1:2
so half life ratio = 2:1
so for getting probability of finding alpha and beta same ratio will be 1:2
a carbon sample from the frame of a picture gives 7 counts of C-14 per minute per gram of carbon . if freshly cut wood gives 15.3 counts of C-14 per minute. calculate the age of frame (t½ of C-14 = 5570 yrs)
(a) 6286 yrs
(b) 5527 yrs
(c) 5570 yrs
(d) 4570 yrs
use t = 2.303/k * log(15.3/7)
k = 0.6932/t1/2
the binding energy per nucleon for C-12 is 7.68 MeV and that for C-13 is 7.47 MeV. calculate the energy required to remove a neutron from C-13
(a) 4.5MeV
(b) 45MeV
(c) 0.45MeV
(d) 0.045MeV
7.47*13-7.68*12 = 97.11-92.16 = 4.5 Mev approx
1gm of 94Pu-239 is an α-emitter with a half life of 24400 yrs. given 1g sample of this plutonium how many α-particles will it emit per second?
(a) 2.27*10^9
(b) 2.27*10^10
(c) 2.27*10^11
(d) 2.27*10^12
dn/dt = kn
so dn = (0.6932/24400*3.1*107)*(1/239)*6.023*1023*1
solve
a radioactive substance (M= 100g/mol) have t½ of 5 days. if today 0.125mg is left over what was its activity 20 days earlier?
(a) 522.8 Ci
(b) 1.93*10^7 Rd
(c) 1.93*10^13 Bq
(d) all of these
20 day means 4 half lifes so today 0.125mg means 0.125*24 = 2gm earlier
so activity dn/dt = kn
solve and convert in required units
a uranium mineral contains U-238 and Pb-206 in the ratio 4:1 by weight. Calculate the age of mineral (t½ for U-238 = 4.5 *10^9 years)
(a) 1.45*10^9 yrs
(b) 16.6*10^9 yrs
(c) 16.6*10^10 yrs
U:Pb = 4:1
taking these ratio as mass
we get the initial mass of U = 4+(1*235/208)
and present mass of U = 4
now use the first order equation of radioactivity