CBSE Class 12-science Answered
4.32 numerical plz
![question image](https://images.topperlearning.com/topper/new-ate/topr_12933646033181238rps20190916214215.jpeg)
Asked by lovemaan5500 | 18 Sep, 2019, 22:02: PM
50% of reaction gets completed in 2 hr. that is, half life period of reaction is 2 hr.
Next half reaction gets completed in 2hr that is (25% half of reamaining 50%) half life period is 2 hr.
So the half life period of reaction is independent of concentration. Hence it is first order reaction.
Also, we can solve this by using equations for first order reaction,
We have,
![straight t subscript bevelled 1 half end subscript space equals space fraction numerator 0.693 over denominator straight k end fraction](https://images.topperlearning.com/topper/tinymce/cache/ce82821b4c56ff020c90228c8f266c0e.png)
We know,
t1/2 = 2 hr
![therefore](https://images.topperlearning.com/topper/tinymce/cache/942eb844c24601f96a83e77dde6aa89c.png)
By using expression for first order reaction,
![straight k space equals fraction numerator 2.303 over denominator straight t end fraction cross times log open parentheses fraction numerator straight A over denominator straight A minus straight X end fraction close parentheses](https://images.topperlearning.com/topper/tinymce/cache/5f3ddc16327e7207fccbf0ecf0c74286.png)
t = 4 hr
A = 100
(A-X) = 100- 75
= 25
![straight k equals fraction numerator 2.303 over denominator 4 end fraction cross times log 100 over 25
straight k equals 0.3466 space hr to the power of negative 1 end exponent](https://images.topperlearning.com/topper/tinymce/cache/76bdea84ca2216b67952584611352797.png)
By using expressions for first order reaction, we get same value of rate constant.
Hence it is confirmed that, it is a first order reaction.
Answered by Varsha | 19 Sep, 2019, 13:12: PM
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