The standard enthalpy change for the following reaction is 232 kJ at 298 K. 2 H2CO(g) 2 C(s, graphite) + 2 H2(g) + O2(g) ΔH° = 232 kJ What is the standard enthalpy change for this reaction at 298 K? C(s, graphite) + H2(g) + 1/2 O2(g) H2CO(g)

 The standard enthalpy change for this reaction is -116 kJ

Explanation:

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

The given chemical reaction is,

Now we have to determine the value of for the following reaction i.e,

According to the Hess’s law, if we reverse the reaction then the will change its sign and if we half the reaction, then the

So, the value for the reaction will be:

Hence, the standard enthalpy change for this reaction is -116 kJ

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.