The reaction A to products is first order in A.

Question

1.) If 2.00 g A is allowed to decompose for 42 min, the mass of A remaining undecomposed is found to be 0.50 g. What is the half-life, t_{1/2}, of this reaction?
2.)Starting with 2.00 g A, what is the mass of A remaining undecomposed after 1.00 h?

Answer 1

1).
ln(No/N) = kt
ln(2/0.5) = k*42
solve for k, then substitute for k in th following:
k = 0.693/t_1/2 and solv for
t_1/2

For 2).
ln(2/N) = k*60
solve for N. Use k from the first part.