A flask is charged with 0.124 mol of A and allowed to react to from B according to the reaction: A(g) -> B(g). the following drata are obtained for [A] as the reaction proceeds:
time: 0.00 10.0 20.0 30.0 40.0
moles of A: 0.124 0.110 0.088 0.073 0.054
A) what is the average rate of disapperance of A between 10s and 20s?
B) what is the avergae rate of disappearance of A between 20s and 40s?
C) what is the average rate of appearance of B between 20s and 30s?
D) How many moles of B are present at 10s?
E) how many moles of B are present at 30s?

Respuesta :

Answer:

A) -0.0022mol/s

B) -0.0017mol/s

C) 1.5x10^{-3}mol/s

D) 0.014molB

E) 0.051molB

Explanation:

Hello, here the answers:

A) Consumption.

[tex]\frac{0.088mol-0.110mol}{40s-20s} =-0.0022mol/s[/tex]

B) Consumption.

[tex]\frac{0.054mol-0.088mol}{40s-20s} =-0.0017mol/s[/tex]

C) Production.

Since the stoichiometric coefficients are 1 for both A and B, the consumed moles of A are equal to the difference between the initial moles of A and the actual moles of A, thus:

[tex]molB_{20s}=0.124mol-0.088mol=0.036molB\\molB_{30s}=0.124mol-0.073mol=0.051molB[/tex]

Now, the rate of appearance:

[tex]r_B=\frac{0.051mol-0.036mol}{30s-20s} =1.5x10^{-3}mol/s[/tex]

Which positive indeed because the moles are being formed.

Another way to find is by doing it directly with the moles of A since the rates are numerically equal but differing in the sign:

[tex]r_B=-r_A=-\frac{0.073mol-0.088mol}{30s-20s} =1.5x10^{-3}mol/s[/tex]

D) Based on the previous analysis:

[tex]molB_{10s}=0.124mol-0.110mol=0.014molB[/tex]

E) Again:

molB_{30s}=0.124mol-0.073mol=0.051molB

Best regards.

The initial number of moles of A of 0.124 moles and the table of values gives the following values;

A) The rate of disappearance of A is 0.0022 moles/s

B) The rate of disappearance of A is 0.0017 moles/s

C) The rate of appearance of B is 0.0015 moles/s

D) 0.014 moles

E) 0.051 moles

How can the average rate of disappearance and number of moles a substance be found from the given table?

A) At 10.0 s, the number of moles present = 0.110 moles

At 20.0 s, the number of moles present = 0.088 moles

Therefore;

[tex]Average \ rate \ of \ disappearance = \mathbf{\dfrac{0.088 - 0.11}{20 - 10}} = -0.0022[/tex]

The average rate of disappearance of A between 10s and 20s is 0.0022 mole/s

B)  At 20.0 s, the number of moles present = 0.088 moles

At 40.0 s, the number of moles present = 0.054 moles

Therefore;

[tex]Average \ rate \ of \ disappearance = \mathbf{ \dfrac{0.054 - 0.088}{40 - 20}} = -0.0017[/tex]

The average rate of disappearance of A between 40s and 20s is 0.0017 mole/s

C) At 20.0 s, the number of moles of B present  = (0.124 - 0.088) moles = 0.036 moles

At 30.0 s, the number of moles of B present = (0.124 - 0.073) moles = 0.051 moles

Therefore;

[tex]Average \ rate \ of \ disappearance = \dfrac{0.051 - 0.036}{30 - 20} = \mathbf{0.0015}[/tex]

The average rate of appearance of B between 30s and 20s is 0.0015 mole/s

D) The number of moles of B present at 10 s is (0.124 - 0.110) moles = 0.014 moles

E) From the table, the number of moles of B present at 30 s are (0.124 - 0.073) moles = 0.051 moles

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