Chemistry In Everyday Life Ques 1
1. Which of the following is a cationic detergent?
[2020]
(a) Sodium stearate
(b) Cetyltrimethyl ammonium bromide
(c) Sodium dodecylbenzene sulphonate
(d) Sodium lauryl sulphate
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Answer:
Correct Answer: 1.(c)
Solution:
(c) For a first order reaction
Total time T = no. of half lives
Give $N_0$ (Original amount) = $1.28 mg/l$
N (amount of substance left after time T) = $ 0.04 {~mg}L^{-1} $
$\begin{aligned} \therefore \frac{0.04}{1.28} & =\left(\frac{1}{2}\right)^{\mathrm{n}} ; \frac{1}{32}=\left(\frac{1}{2}\right)^{\mathrm{n}} ;\left(\frac{1}{2}\right)^5=\left(\frac{1}{2}\right)^{\mathrm{n}} \\ n & =5 \\ T & =5 \times 138=690\end{aligned}$
BETA
