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Chemistry homework Help


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Urgenthomework provides Homework Help in Chemistry. Chemistry, the study of matter is one of the most complex of all subjects and needs deep and thorough understanding and hours of deep concentration and study to master it. It can not be understood by just reading and needs skillful explanation to make the grasping easier. Though it is a Science but it has a lot of application in everyday life too. Chemistry Tutors are not found easily as the subject can not be understood by all with ease. Chemistry Homework isn’t easy for Students and they do find difficulty in understanding with just the class notes. Students mostly look out for High School Chemistry Homework Help as they need extra guidance in their Chemistry Homework. Organic Chemistry, periodic tables and the chemical structures remain to be a mystery with most of the Students and they thus need Chemistry Homework Help.


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Chemistry Assignment Help


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Topics of Chemistry to Get Chemistry Homework Help Services Online


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Question 1: (1 point)

The reaction
2I(aq) + H3AsO4(aq) + 2H+(aq) ---> I2(aq) + H3AsO3(aq) + H2O(l)
proceeds via the mechanism below. According to the given mechanism, what is the correct expression for the rate of consumption of H3AsO4?

 

 

Step 1
(reversible):
  

H3AsO4 + H+   ⇄   H4AsO4+   

fast in both directions,
with rate constants k1 and k-1

 

 

 

Step 2
(irreversible):

H4AsO4+ + I  ⟶  H3AsO3 + HOI  

slow, with rate constant k2

 

 

 

Step 3
(irreversible):
  

HOI + I + H+  ⟶  I2 + H2O

fast, with rate constant k3

 

 

(a)

Rate=k [I]2 [H3AsO4] [H+]2 / [H3AsO3]

 

(b)

Rate = k [I]2 [H3AsO4] [H+]

 

(c)

Rate = k [I] [H3AsO4] [H+]2

 

(d)

Rate = k [I]2 [H3AsO4] [H+]2

 

(e)

Rate = k [I]2 [H3AsO4]

 

(f)

Rate = k [I] [H3AsO4] / [H+]

 

(g)

Rate = k [I] [H+]2

 

(h)

Rate=k [H3AsO3] / ([I]2 [H3AsO4] [H+]2)

 

(i)

Rate = k [I] [H3AsO4]

 

(j)

Rate = k [H3AsO4] [H+]

 

(k)

Rate = k [I]2 [H+]

 

(l)

Rate = k [I] [H3AsO4] [H+]

Question 3: (1 point)

The reaction X + Y → products were studied using the method of initial rates. The initial rate of consumption of X was measured in three different experiments. Data are provided below.

Expt

[X]o
(in mol/L)

[Y]o
(in mol/L)

Initial Rate
(in mol L
-1 s-1)

1

0.700

0.400

6.608

2

2.10

0.400

19.82

3

0.700

1.20

59.47

 

What is the order of the reaction with respect to X?  ____________  (Enter an integer.)

What is the order of the reaction with respect to Y?  ____________  Enter an integer.) 

Specify the units of k by giving the appropriate powers of mol, L and s:

The power of mol is  ____________  (Enter an integer.)

The power of L is  ____________  (Enter an integer.)

The power of s is  ____________  (Enter an integer.)


Question 4: (1 point)

Consider the following reacton:

3 A(aq) + 4 B(aq) → 4 C(aq) + 4 D(aq)

What is the rate of production of C, in mol L-1 s-1, if the rate of consumption of A is 0.790 mol L-1 s-1?

Enter your answer accurate to three significant figures. Do not include units. If necessary, use exponential notation (e.g. 1.23E-3 for 1.23x10-3).


Question 5: (1 point)

The decomposition reaction, X → products, is zeroth-order with a rate constant k=0.0811 mol L-1 s-1. How long will it take for the decomposition to be 95% complete if the initial concentration of X is 1.25 mol/L?

Give your answer in seconds, accurate to three significant figures. Do not include units as part of your answer.


Question 6: (1 point)

The decomposition reaction X → products were studied as a function of time. Data are given in the table below.

 

time (in s)

[X] (in mol/L)

0.0

1.650

3.20E2

0.8259

6.40E2

0.5508

9.60E2

0.4131

1.28E3

0.3306

What is the value of the rate constant? (Give your answer accurate to three significant figures. Do not give units as part of your answer, but use concentrations in mol/L and time in seconds.)


Question 7: (1 point)

Consider the data below for the reaction X → products. (Hint: You will have to determine the order of the reaction before you can answer parts (b)-(d) of this question.)

 

Time (in seconds)

[X] (in mol/L)

0

1.5500

3.60E2

0.7755

7.20E2

0.5171

1.08E3

0.3878

1.44E3

0.3103

 

For parts (a), (c), and (d): Enter your answer accurate to three significant figures. Do not include units in your answer, but use concentrations in mol/L and time in seconds.

(a) What is the average rate of consumption of X between 3.60E2 s and 1.08E3 s?  ____________ 

(b) What is the order of the reaction? (Enter an integer, or a fraction, e.g. 1/2, 3/2, etc.)  ____________ 

(c) What is the value of the rate constant, k?  ____________ 

(d) What is the instantaneous rate of consumption of X at 1.08E3 s?  ____________ 


Question 8: (1 point)

The activation energy, Ea, for a second-order reaction, X ---> products, is most readily obtained from the slope of a plot of

 

 

(a)

[X] versus time

 

(b)

k versus 1/T, where T is the temperature in K

 

(c)

ln k versus time

 

(d)

k versus T, where T is the temperature in K

 

(e)

ln k versus T, where T is the temperature in K

 

(f)

[X]2 versus time

 

(g)

1/[X] versus time

 

(h)

Rate versus time

 

(i)

ln[X] versus time

 

(j)

ln k versus 1/T, where T is the temperature in K



Question 9: (1 point)

Fill in the blanks:

The elementary reaction A(aq) + B(aq) --> C(aq) is exothermic in the forward direction. What happens to k 1, k -1, and Kc when the temperature increases? (In each case, type one of the following: increasesdecreases, or remains the same.

(a) k : ____________ .

(b) k -1 : ____________ .

(c) K : ____________ . 


Question 10: (1 point)

For the elementary process below, the activation energy is 41 kJ/mol and the enthalpy change is 22 kJ/mol. What is Ea for the reverse process, in kJ/mol?

A + B ⇌ AB


Question 11: (1 point)

A reaction has a first-order rate constant of 4.09x10-5 s-1 at 25oC and 0.00141 s-1 at 77oC. What is the value of the rate constant at 55oC?

Enter your answer in units of s-1, accurate to three significant figures. Do not include units as part of your answer. (Enter 1.23x10-3 as 1.23e-3.)

Question 12: (1 point)

A catalyst decreases the activation energy of a given reaction by exactly 13 kJ/mol.  By what factor does the reaction rate increase at 25oC when the catalyst is used? Assume that the Arrhenius pre-exponential factor, A, is the same for the catalyzed and uncatalyzed reactions.

Enter your answer accurate to three significant figures. Do not include units as part of your answer. (Enter 1.23x10-3 as 1.23e-3.)

Topics in Chemistry

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