which statement about △hf is true? it is positive when the bonds of the product store more energy than those…
which statement about △hf is true? it is positive when the bonds of the product store more energy than those of the reactants. it is zero for any pure substance in its standard state. it is negative when a compound forms from elements in their standard states. it is zero for any compound that is in the liquid state.
Answer
Brief Explanations:
- For the first option: The standard - enthalpy of formation ($\Delta H_f$) is positive when the bonds of the product store more energy than those of the reactants. This is because energy is absorbed during the formation of the product from its elements in their standard states.
- For the second option: $\Delta H_f$ is zero for an element in its standard state, not for any pure substance. For example, a pure compound has a non - zero $\Delta H_f$.
- For the third option: $\Delta H_f$ is negative for an exothermic formation reaction, but not for all reactions where a compound forms from elements in their standard states. There are endothermic formation reactions as well.
- For the fourth option: $\Delta H_f$ is not zero for any compound in the liquid state. Compounds in the liquid state have non - zero formation enthalpies depending on their chemical composition and the elements from which they are formed.
Answer:
It is positive when the bonds of the product store more energy than those of the reactants.