In a reversible reaction, the forward reaction takes place {after, before, simultaneously} the reverse reaction. such a reaction, on reaching equilibrium, will have

In a reversible reaction, the forward reaction takes place simultaneously the reverse reaction. Such a reaction, on reaching equilibrium, will have equal rate of going forward and going backward.

Explanation: It is a reaction in which the reactants reacts to give products and products reacts to give the reactants back simultaneously.

In the above reaction reactants A and B reacts together to give products C and D, and vice versa.

In these reaction rate of reaction going forward is equal the rate of reaction going backward at the equilibrium.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally