If adenine is 31% in DNA, calculate the percentage of cytosine. Explain briefly.
Adenine pairs with thymine (31% each), totaling 62\%. Cytosine and guanine share the remaining 38%. Therefore, cytosine is 19%, following Chargaff’s rule, where purines (adenine, guanine) always pair with pyrimidines (thymine, cytosine).
A certain reaction is 50 complete in 20 minutes at 300 K and the same reaction is 50 complete in 5 minutes at 350 K. Calculate the activation energy if it is a first order reaction. Given: \[ R = 8.314 \, \text{J K}^{-1} \, \text{mol}^{-1}, \quad \log 4 = 0.602 \]