Q50.
Ans:5.
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dear student
Kt = 2.303log ( p_i/( 2​​​​​p​​_i-p_t ) )
K*10= 2.303log (20/(-40)
K*10= 2.303 log2
K= 2.303*0.3/10
K=0.069
t_1/2=0.69/k
      =10 minutes

regards