Physical Chemistry Answers

the ionic product of water at 80°C is 2.44×10^-13. what are the concentrations of hydroxide ion and hydronium ion in pure water at 80°C?

Question 19 : Which of the following statements about the kinetics of the reaction
H
2
(
g
)
+
B
r
2
(
g
)
→
2
H
B
r
(
g
)
H2(g)+Br2(g)→2HBr(g)
is definitely true?
The presence of hydrogen bromide, HBr, inhibits the rate of the reaction
The reaction is first order with respect to bromine, Br2.
It is not possible to determine anything about the kinetics of the reaction from the stoichiometry.
The reaction is second order overall.

Question 20 : Rate of reaction is defined as the
None of the above
Rate of change of conc. of product only
Rate of change of conc. of reactant only
Rate of change of concentration Of either reactant or product per unit time

Question 16 : A beaker with a mixture of ice and water is maintained at equilibrium:
H
2
O
(
s
)
+
h
e
a
t
→
H
2
O
(
l
)
H2O(s)+heat→H2O(l)
; If the temperature of the system is decreased:
No change occurs
The container cacks
Ice melts to form liquid water (shift to the right)
Water freezes to form ice (shifts to the left)

Question 17 : The term — dx/dt in the rate expression refers to the
Average rate of the reaction
increase in concentration of the reactants
instantaneous rate of the reaction
Change in concentration of the reactants with time

Question 18 : Rusting of iron Is an example of________ reaction
Fast
Slow
explosive
Moderate

Question 13 : The minimum additional energy, above the average internal energy, which the reacting molecules must possess so that their collision result in a reaction is known as
Thermodynamic energy
Activation energy
Kinetic energy
Threshold energy

Question 14 : The factor that affects the rate of reaction is
Catalyst
All of these
Temperature of the reactants
Nature and concentration of the reactants

Question 15 : In a reaction:
2
A
→
B
+
2
C
2A→B+2C
, which of the statement is true?
Rate of formation of B = Rate of disappearance of A
Rate of disappearance of A = Rate of formation of C
Rate of disappearance of A = Rate of formation of B
Rate of formation of C= Rate of formation of B

Question 10 : The reactions catalyzed by sunlight are called ____________ reactions
Exothermic
Sun-lighted
Endothermic
photochemical

Question 11 : The reaction below is exothermic:
2
S
O
2
(
g
)
+
O
2
(
g
)
→
2
S
O
3
(
g
)
2SO2(g)+O2(g)→2SO3(g)
. Le Chatelier's Principle predicts that __________ will result in an increase in the number of moles of
S
O
3
SO3
(g) in the reaction container.
decreasing the pressure
increasing the volume of the container
increasing the pressure
removing some oxygen

Question 12 : When extra
N
H
3
NH3
is added to the following system at equilibrium:
3
H
2
(
g
)
+
N
2
(
g
)
→
2
N
H
3
(
g
)
3H2(g)+N2(g)→2NH3(g)
, what happens?
Concentration of hydrogen decreases, but that of hydrogen increases
No change occurs
In order to restore equilibrium, the reaction shifts left, toward reactants
In order to restore equilibrium, the reaction shifts right, toward product

Question 6 : Powdered marble reacts more rapidly with HCl than the chips of marble because:
Surface area of powdered marble is more that of chips of marble and hence there is more collisions between the molecules of reactants
Number of molecules increases.
Energy of activation decreases
Marble chips will not react with HCl

Question 7 : In the reaction:
2
B
→
P
r
o
d
u
c
t
2B→Product
; the rate equation is: Rate = k[B]. If the concentration of ‘B’ is doubled, the rate of reaction will increase by a multiple of
Four
Three
None of these
Two

Question 8 : For a reaction:
2
H
2
+
2
N
O
→
2
H
2
O
+
N
2
2H2+2NO→2H2O+N2
the rate law is
R
=
K
[
H
2
]
[
N
O
]
2
R=K[H2][NO]2
The Order of the reaction is?
2
3
0
1

Question 9 : The rate of chemical reaction
Remains constant as reaction proceeds
Increases as the reaction proceeds
Decreases as the reaction proceeds
Both (a) and (b)

Question 4 : Equilibrium is a state of dynamic molecular behaviour, meaning that
reactants turn into products and products turn into reactants at different rates.
reactants turn into products and products turn into reactants at equal rates
products continually turn into reactants at a progressively faster rate.
the reaction eventually comes to a stop.

Question 5 : Milk sours more rapidly in summer than in winter because
in summer, the temperature Is high due to which effective collisions increase and hence the rate of reaction becomes fast
none of the above
in summer, the energy of activation decreases and hence the of reaction becomes fast
in winter, number of molecules per unit volume increases and hence the rate of reaction becomes fast

Question 19 : A statement of the second law of thermodynamics is that
energy is conserved in a chemical reaction.
the entropy of the universe is continually increasing.
the enthalpy of reaction is the difference between product and reactant enthalpies.
spontaneous reactions are always exothermic.

Question 20 : The temperature remains constant as energy is added to a substance. How may the substance be changing?
From a gas to a solid
Change in the amoung of kinetic energy
From a liquid to a gas
From a liquid to a solid

Estimate the freezing point if 150 cm3 of water sweetened with 7.5 g of sucrose