The rate constant for this first-order reaction is 0.0265 s − 1 at 300 °C. A ⟶ products If the initial mass of A is 16.74 g, calculate the mass of A remaining after 1.27 min.

Answer : The mass of A remaining after 1.27 min is, 13.7 grams

Explanation :

Expression for rate law for first order kinetics is given by:

where,

k = rate constant  =

t = time passed by the sample  = 1.27 min = 76.2 s   (1 min = 60 s)

a =  initial amount of the reactant  = 16.74 g

a - x = amount left after decay process = ?

Now put all the given values in above equation, we get

Therefore, the mass of A remaining after 1.27 min is, 13.7 grams

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"