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If 30cm\(^3\) of oxygen diffuses through porous plug in 7s, how long will it take...

Chemistry
JAMB 1997

If 30cm\(^3\) of oxygen diffuses through porous plug in 7s, how long will it take 60 cm\(^3\) of chlorine to diffuse through the same plug?

  • A. 12s
  • B. 14s
  • C. 21s
  • D. 30s
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Correct Answer: Option C
Explanation

Given:

t\(_c\) = ?  V\(_c\) = 60cm\(^3\) ,  M\(_c\) = 35.5 x 2 = 71

t\(_o\) = 7s;  V\(_o\) = 30cm\(^3\) ,  M\(_o\) = 16 x 2 = 32

According to Graham's law of diffusion, R ∝  1/√M

                                            \(\frac{R_o}{R_c}\) = \(\sqrt{\frac{M_c}{M_o}}\)

                                                 AlsoRate of diffusion =  \(\frac{Volume}{time}\)

\(\frac{R_o}{R_c}\) =  \(\frac{V_o}{t_o}\) ÷ \(\frac{V_c}{t_c}\) =  \(\frac{V_o}{t_o}\) X \(\frac{t_c}{V_c}\)

Therefore,  \(\frac{V_o}{t_o}\) X \(\frac{t_c}{V_c}\) =  \(\sqrt{\frac{M_c}{M_o}}\)

                 \(\frac{{30}\times{t_o}}{{7}{60}}\) = \(\sqrt{\frac{71}{32}}\)

                 \(\frac{t_c}{14}\) = 1.489

                 t\(_c\) = 14 x 1.489

                 t\(_c\) = 20.846

                 t\(_c\) = 21s


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