If 75 % of a first-order reaction was completed in 90 minutes, 60 % of the same reaction would be completed in approximately (in minutes):

(Take : log 2 = 0.30 ; log 2.5 = 0.40)

1. 50 min

2. 60 min

3. 70 min

4. 65 min

Decomposition of H₂O₂ follows a first order reaction. In fifty minutes the concentration of H₂O₂ decreases from 0.5 to 0.125 M in one such decomposition. When the concentration of H₂O₂ reaches 0.05 M, the rate of formation of O₂ will be : 

ln 4=1.39

1. 7×10^–2 M min^–1
2. 7×10^–4 M min^–1
3. 2.66×10^–2 M min^–1 
4. 2.66 ×10^–4 M min^–1

Which of the following is the time required for 99% completion of a first-order reaction if its half-life is 6.93 minutes \((\log 2 = 0.301)\)?

1. 230.3 minutes

2. 23.03 minutes

3. 46.06 minutes

4. 460.6 minutes

Which of the following is the mass of a radioisotope remaining undecayed after 24 hours, if its half-life is 4 hours and the initial mass is 200 g?

1. 1.042 g
2. 2.084 g
3. 3.125 g
4. 4.167 g

Gaseous cyclobutene isomerizes to butadiene in a first-order process which has a 'k' value of
3.3 × 10^–4s^–1 at 153 ºC. The time in minutes it takes for the isomerization to proceed 40 % to
completion at this temperature is _____. (Rounded off to the nearest integer)

1. 26 min

2. 30 min

3. 22 min

4. 24 min

Sucrose hydrolysis in an acidic solution into glucose and fructose follows the first-order rate law with a half-life of 3.33 h at 25°C. After 9 h, the fraction of sucrose remaining is f. The value of  \(log(\frac{1}{f})\) is A×10^-2 . The value of A is:
(Rounded off to the nearest integer) [Assume : ln 10 = 2.303, ln 2 = 0.693]
1. 78
2. 81
3. 85
4. 75

Half-life of substance A following first order kinetics is 5 days. Starting with 100g of A, the amount left after 15 days will be: