The total enthalpies of reactants and products are $H_R$ and $H_P$ respectively. For an exothermic reaction,which of the following is true?

If the value of $\Delta H$ in a reaction is positive,then the reaction is called

The enthalpy change for the reaction,$C_{2}H_{6(g)} \to 2C_{(g)} + 6H_{(g)}$ is $X \ kJ$. The bond energy of $C-H$ bond is :-

Which substance has a standard molar enthalpy of formation equal to zero at $298 \ K$?

Which of the following equations correctly represents the standard heat of formation $(\Delta H_f^o)$ of methane?

The total enthalpy change in a chemical reaction is equal to the algebraic sum of the enthalpy changes of the individual steps of the reaction. This statement is associated with which scientist?