Henry’s law is a gas law which states that at the amount of gas that is dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid when the temperature is kept constant. The constant of proportionality for this relationship is called Henry’s law constant (usually denoted by ‘ K H ‘). Henry’s law does not hold true when gases are placed under extremely high pressure.

Derive an integrated rate equation for a first order reaction.

Let us, consider a unimolecular first order reaction represented by the general equation, A → Product At t = 0 a 0 At t = t a - x x The initial concentration of A is a mole L - 1 and its concentration after time t is ( a – x ) mole L - 1 . This means during the time interval t , x mole L – 1 of A has reacted. The rate of reaction at any time t is given by the following first order kinetics. dx dt = k a - x where k is the rate constant of the reaction. dx a - x = kdt This is differential rate equation and can be solved by integration. ∫ dx a - x = k ∫ dt - ln a - x = k . t + C . . . . . ( 1 ) where C is integration constant. The constant C can be evaluated by applying the initial condition of the reaction i.e. when t = 0 , x = 0 . Putting these in equation (1), we get C = – ln a Putting the value of C in equation (1), we get – ln ( a – x ) = k . t – lna k = 1 t ln a a - x = 2 . 303 t log a a - x . . . . . ( 2 ) Equation (2) integrated rate equation for a first order reaction.