Can anyone me with this ! my exam is day after tomorrow

a. Lithium is in its standard state

b.

c.

Explanation:

a. Elements in their standard states at room temperature and 1 atm pressure would have an enthalpy of formation of 0 kJ/mol. Lithium is metal at standard conditions, so its enthalpy of formation is 0 kJ/mol.

b. The equation representing the formation of a compound should following the rules below:

We should, hence, form 1 mol of LiOH from the following species:

We obtain the following equation:

c. Firstly, write the equation for the enthalpy of formation of water using the guidelines in (b):

Now given the equation:

As well as:

Notice that multiplying reaction (2) by 2, multiplying reaction (3) by 2, multiplying reaction (1) by -2 (that is, multiplying by 2 and reversing it) and adding them together will yield the target equation:

According to Hess's Law, we will perform the same steps with the enthalpy values and we will add them to get the final enthalpy value:

c is the answer because when something is left after something evaporates that shows the chemical change.