The half life for the radioactive decay of potassium-40 to argon-40 is 1.26 x 10^9 years. Suppose nuclear chemical analysis shows that there is 0.367 mmol of argon-40 for every 1.000 mmol of potassium-40 in a certain sample of rock. Calculate the age of the rock.
Round your answer to 2 significant digits.

Iknow #2 is d. i just need to know why

Butadiene undergoes a reaction at a certain temperature in the gas phase as follows: 2c4h6(g) --> c8h12(g) the following data were collected for this reaction: time (min) [c4h6] (m) 0 0.36 15 0.30 30 0.25 48 0.19 75 0. determine the order of the reaction and the rate constant. 1st order and k = 4.3x10 -4 s-1 1st order and k = 2.3x10-4 s-1 2nd order and k = 4.3x10-4 s-1 2nd order and k = 2.3x10-4 s-1 zero and k = 4.3x10-4 s-1

If 22.5 liters of oxygen reacted with excess of hydrogen, how many liters of water vapor could be produced?