For the simple decomposition reaction AB(g) → A(g) + B(g) rate = k[AB]2 and k = 0.20 L/mol·s. If the initial concentration of AB is 1.50 M, what is [AB] after 10.3 s?

Respuesta :

Answer:

[AB] = 0.66M

Explanation:

rate = change in concentration/time

Initial concentration of AB = 1.5M

Let the concentration of AB after 10.3s be y

Therefore, rate = 1.5 - y/10.3

The rate equation is given as

rate = k[AB]^2 = 0.2y^2

0.2y^2 = 1.5 - y/10.3

2.06y^2 = 1.5 - y

2.06y^2 + y - 1.5 = 0

Using the quadratic formula

y = [-1 + or - √(1^2 -4×2.06×-1.5)/2(2.06)]

The value of y must be positive

y = (-1 + √13.36)/4.06 = -1+3.66/4.06 = 2.66/4.06 = 0.66

Concentration of AB after 10.3s is 0.66M

For the simple decomposition reaction, the concentration of reactant i.e. AB after 10.3 sec is 0.66M.

What is rate of any reaction?

Rate of any reaction is defined as the rate of change of concentration with respect to the time.

Given reaction is:
AB(g) → A(g) + B(g)

Rate for this reaction is 0.20 L/mol·s, which can be calculated as k[AB]².

Initial concentration of AB = 1.50 M (given)

Let, concentration of AB after 10.3 sec = y

So, Rate of the reaction can be expressed as = 1.50 - y/10.3  ...........(i)

Let we calculate the rate on the basis of given equation = 0.20 [y]² ........(ii)

From (i) & (ii) equation,

0.20 [y]² = 1.50 - y/10.3

2.06 [y]² = 1.50 - y

2.06 [y]² + y - 1.50 = 0

We can find the value of y by using the formula of quadratic equation as :

y = [-1 + or - √(1^2 -4×2.06×-1.5)/2(2.06)]

[tex]\[\frac{{{\rm{ - 1 + or - }}\sqrt {{{{\rm{(1)}}}^{\rm{2}}}{\rm{ - 4 \times 2}}{\rm{.06 \times 1}}{\rm{.50}}} }}{{{\rm{2 \times 2}}{\rm{.06}}}}{\rm{ = 0}}\][/tex]

y = + or - 0.66

But value of concentration is never zero.

So, y = 0.66 M

Hence, the concentration of AB after 10.3 sec is 0.66M.

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