In a first-order decomposition reaction, 50,0 % of a compound decomposes in 10,5

Question

In a first-order decomposition reaction, 50,0 % of a compound decomposes in 10,5 min. (a) What is the rate constant of the reaction? (b) How long does it take for 75,0% of the compound to decompose? 5.13. A decomposition reaction has a rate constant of 0,0012 yr (a) What is the half-life of the reaction? (b) How long does it take for [reactant] to reach 12,5 % of its original value? 5.14. The reaction 2NOCI(g) 2NO(8)+Cl2(g) has an Ea of 1,00-102 kJ/mol and a rate constart of 0,286 s at 500 K. What is the rate constant at 490 K? SS. Determine the reaction rate temperature coefficient, if at temperature 22 C k 1 s and at 45 5.16. The rate constant of a reaction is 2 Umois) at 88 °C and 6 L(mols) at 101 °C. At what temperature the rate constant will be 20? 57. Calculate by using the Van't Hoff rule what temperature change is needed to decrease the reaction rate 48 times, if y is 2,7. 5r8. No changes have been noticed while storing medicine within 18 days at 80 °C. Is it possible to store medicine within 3 years at 20 °c?

Explanation / Answer

(5.12)

t1/2 = 10.5 min

(a)

Using relation:

k = 0.693/t1/2 = 0.693/10.5 = 0.066 min-1

(b)

For 75% decomposition, it will take two half lives.

First half life will reduce it by 50%.

Second half life will reduce the remaining 50% to 25%.

So totally we get 75% decomposition in two half lives.

So, time required = 2*10.5 = 21 min

Hope this helps !

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