CHEM120: question and answers
The first step in the production of nitric acid is the combustion of ammonia: 4NH3
(g) + 5O2 (g) ⟶ 4NO(g) + 6H2 O(g) Write the equations that relate the rates of
consumption of the reactants and the rates of formation of the products.
Considering the stoichiometry of this homogeneous reaction, the rates for the
consumption of reactants and formation of products are: − 1 4 Δ[NH3 ] Δt = − 1 5 Δ ⎡
⎣O2 ⎤ ⎦ Δt = 1 4 Δ[NO] Δt = 1 6 Δ ⎡ ⎣H2 O ⎤ ⎦ Δt
The rate of formation of Br2 is 6.0 × 10−6 mol/L/s in a reaction described by the
following net ionic equation: 5Br− + BrO3 − + 6H+ ⟶ 3Br2 + 3H2 O Write the
equations that relate the rates of consumption of the reactants and the rates of
formation of the products.
: − 1 5 Δ[Br−] Δt = − Δ[BrO3 −] Δt = − 1 6 Δ[H +] Δt = 1 3 Δ[Br2 ] Δt = 1 3 Δ[H2 O] Δt
If the rate of decomposition of ammonia, NH3, at 1150 K is 2.10 × 10−6 mol/L/s,
what is the rate of production of nitrogen and hydrogen?
1.05 × 10−6 mol/L/s, N2 and 3.15 × 10−6 mol/L/s, H2
In a transesterification reaction, a triglyceride reacts with an alcohol to form an
ester and glycerol. Many students learn about the reaction between methanol
(CH3OH) and ethyl acetate (CH3CH2OCOCH3) as a sample reaction before
studying the chemical reactions that produce biodiesel: CH3 OH + CH3CH2
OCOCH3 ⟶ CH3 OCOCH3 + CH3CH2 OH The rate law for the reaction between
methanol and ethyl acetate is, under certain conditions, determined to be: rate = k
⎡ ⎣CH3 OH⎤ ⎦ What is the o
order in CH3OH = 1; order in CH3CH2OCOCH3 = 0; overall order = 1
Iodine-131 is a radioactive isotope that is used to diagnose and treat some forms
of thyroid cancer. Iodine-131 decays to xenon-131 according to the equation: I-
131 ⟶ Xe-131 + electron The decay is first-order with a rate constant of 0.138 d
−1 . How many days will it take for 90% of the iodine−131 in a 0.500 M solution of
this substance to decay to Xe-131?
16.7 days
If the initial concentration of butadiene is 0.0200 M, what is the concentration
remaining after 20.0 min?
0.0195 mol/L
The zero-order plot in Figure 17.11 shows an initial ammonia concentration of
0.0028 mol L −1 decreasing linearly with time for 1000 s. Assuming no change in
this zero-order behavior, at what time (min) will the concentration reach 0.0001
mol L−1?
35 min
The first-order radioactive decay of iodine-131 exhibits a rate constant of 0.138 d
−1 . What is the half-life for this decay?
5.02 d.
What is the half-life (min) for the thermal decomposition of ammonia on tungsten
18 min
The first step in the production of nitric acid is the combustion of ammonia: 4NH3
(g) + 5O2 (g) ⟶ 4NO(g) + 6H2 O(g) Write the equations that relate the rates of
consumption of the reactants and the rates of formation of the products.
Considering the stoichiometry of this homogeneous reaction, the rates for the
consumption of reactants and formation of products are: − 1 4 Δ[NH3 ] Δt = − 1 5 Δ ⎡
⎣O2 ⎤ ⎦ Δt = 1 4 Δ[NO] Δt = 1 6 Δ ⎡ ⎣H2 O ⎤ ⎦ Δt
The rate of formation of Br2 is 6.0 × 10−6 mol/L/s in a reaction described by the
following net ionic equation: 5Br− + BrO3 − + 6H+ ⟶ 3Br2 + 3H2 O Write the
equations that relate the rates of consumption of the reactants and the rates of
formation of the products.
: − 1 5 Δ[Br−] Δt = − Δ[BrO3 −] Δt = − 1 6 Δ[H +] Δt = 1 3 Δ[Br2 ] Δt = 1 3 Δ[H2 O] Δt
If the rate of decomposition of ammonia, NH3, at 1150 K is 2.10 × 10−6 mol/L/s,
what is the rate of production of nitrogen and hydrogen?
1.05 × 10−6 mol/L/s, N2 and 3.15 × 10−6 mol/L/s, H2
In a transesterification reaction, a triglyceride reacts with an alcohol to form an
ester and glycerol. Many students learn about the reaction between methanol
(CH3OH) and ethyl acetate (CH3CH2OCOCH3) as a sample reaction before
studying the chemical reactions that produce biodiesel: CH3 OH + CH3CH2
OCOCH3 ⟶ CH3 OCOCH3 + CH3CH2 OH The rate law for the reaction between
methanol and ethyl acetate is, under certain conditions, determined to be: rate = k
⎡ ⎣CH3 OH⎤ ⎦ What is the o
order in CH3OH = 1; order in CH3CH2OCOCH3 = 0; overall order = 1
Iodine-131 is a radioactive isotope that is used to diagnose and treat some forms
of thyroid cancer. Iodine-131 decays to xenon-131 according to the equation: I-
131 ⟶ Xe-131 + electron The decay is first-order with a rate constant of 0.138 d
−1 . How many days will it take for 90% of the iodine−131 in a 0.500 M solution of
this substance to decay to Xe-131?
16.7 days
If the initial concentration of butadiene is 0.0200 M, what is the concentration
remaining after 20.0 min?
0.0195 mol/L
The zero-order plot in Figure 17.11 shows an initial ammonia concentration of
0.0028 mol L −1 decreasing linearly with time for 1000 s. Assuming no change in
this zero-order behavior, at what time (min) will the concentration reach 0.0001
mol L−1?
35 min
The first-order radioactive decay of iodine-131 exhibits a rate constant of 0.138 d
−1 . What is the half-life for this decay?
5.02 d.
What is the half-life (min) for the thermal decomposition of ammonia on tungsten
18 min
