Question 11
Which of the following are nucleophiles?
a)
H
+
b)
H
3
O
+
c)
CO
2
d)
AlCl
3
e)
NH
3
Correct Answer:
e) NH
3
Explanation:
Generally, electron pair donors are called as nucleophiles. In the case of ammonia, it has a lone of
pair of electrons. So, it can donate the electron to the other atoms. But, the rest of the atoms can't
donate a pair of electrons instead they can accept a pair of electrons. So, except ammonia all the
other molecules above are known as electrophiles.
Question 12
The ratio of relative abundance of two molecular ion peaks of a chlorine atom in mass
spectroscopy is
a)
M
+
: (M+2) = 1:3
b)
M
+
: (M+2) = 3:1
c)
M
+
: (M+2) = 1:2
d)
M
+
: (M+2) = 2:1
e)
M
+
: (M+2) = 1:1
Correct Answer:
b) M
+
: (M+2) = 3:1
Explanation:
The ratio of relative abundance of two molecular ion peaks of a chlorine atom in mass spectroscopy
is M
+
: (M+2) = 1:3, because the natural abundance of chlorine is higher than other elements. The
natural abundance of chlorine is Cl
35
- 75.77% and Cl
37
t- 24.23%.
Question 13
Compound A reacts by first order kinetics. The rate constant of the reaction is 0.45 sec
-1
. Calculate
the half-life of the compound A in the reaction.
a)
4.62 seconds
b)
3.08 seconds
c)
1.54 seconds
d)
2.25 seconds
e)
0.9 seconds
Correct Answer:
c) 1.54 seconds
