Which of the following standard enthalpy of formation values are not zero at 25°C? (Select all that apply.)

H2(g)
N2(g)
Au(s)
Be(s)
H20(g)
Ne(g)

To determine which of the following standard enthalpy of formation values are not zero at 25°C, we can refer to standard enthalpy of formation tables or use the principles of formation enthalpies.

The standard enthalpy of formation (ΔHf) is the change in enthalpy when one mole of a substance is formed from its elements in their standard states at a specified temperature and pressure.

At 25°C, the standard states of elements are as follows:
- Gaseous elements: H2(g), N2(g), Ne(g)
- Solid elements: Au(s), Be(s)

From the given options:
- H2(g) and N2(g) correspond to gaseous elements, so their standard enthalpy of formation values are not zero at 25°C.
- Au(s) and Be(s) correspond to solid elements, so their standard enthalpy of formation values are generally considered zero.
- H2O(g) and Ne(g) correspond to gaseous elements, so their standard enthalpy of formation values are not zero at 25°C.

Therefore, the substances with non-zero standard enthalpy of formation values at 25°C are:
- H2(g)
- N2(g)
- H2O(g)
- Ne(g)

To determine which of the standard enthalpy of formation values are not zero at 25°C, we can consult a table of standard enthalpy of formation values.

Standard enthalpy of formation (ΔHf°) is the change in enthalpy that occurs when one mole of a substance is formed from its elements in their standard states, with all reactants and products also in their standard states, and all at a specified temperature.

Based on the standard enthalpy of formation values, the substances that have non-zero values at 25°C are:

- H2(g) (hydrogen gas)
- N2(g) (nitrogen gas)
- H2O(g) (water vapor)
- Ne(g) (neon gas)

Au(s) (gold metal) and Be(s) (beryllium metal) are not included because they are elements in their standard states, and standard enthalpy of formation values for elements in their standard states are defined as zero.

So, the substances that have non-zero standard enthalpy of formation values at 25°C are H2(g), N2(g), H2O(g), and Ne(g).

The ones at standard state will be zero. Those not at standard state will not.