JEE Advanced 2020 Full Test 1 Paper 2

For Q using steady state concept
Rate of appearance of Q= rate of disappearance of Q
K1[P]=K2[Q]
Number of nuclei of Q=‌

k1

k2

×no. of nuclei of P=‌

10∕60

1000

×6×1023=1020
For R, since rate constant is very high for second step than first step Number of nuclei of R= Number of nuclei of P disintegrated =6×1023