CO + 2H2 ---> CH3OH

Change in heat= -90.7 KJ/mol
Calculate the mass of hydrogen formed when the change in heat is +90.7 KJ/mol

2 moles of H2= 1 mole of CH3OH
2(1x2)g
2(2)g
=4g
Am I correct?

That looks ok to me.

To calculate the mass of hydrogen formed when the change in heat is +90.7 KJ/mol, you can use the stoichiometry of the reaction and the molar mass of hydrogen (H2).

Given:
Change in heat = -90.7 KJ/mol

The balanced equation for the reaction is:
CO + 2H2 ---> CH3OH

From the balanced equation, we can see that 2 moles of H2 are required to produce 1 mole of CH3OH. This means that the molar ratio between H2 and CH3OH is 2:1.

To solve the problem, you can set up a proportion using the molar ratio and the change in heat values. Since the change in heat is given as a negative value (-90.7 KJ/mol), we need to consider the absolute value when calculating the mass.

Proportion:
(2 moles H2 / -90.7 KJ) = (x moles H2 / +90.7 KJ)

Let's solve for "x", the number of moles of H2 when the change in heat is +90.7 KJ/mol.

Cross-multiplying and simplifying the equation, we get:
x moles H2 = (2 mol H2 * +90.7 KJ) / -90.7 KJ

The KJ units cancel out, and the answer would be in moles. This calculation gives us the number of moles of H2 produced when the change in heat is +90.7 KJ/mol.

To convert the moles of H2 to grams, we need to multiply by the molar mass of H2. The molar mass of hydrogen (H2) is approximately 2 g/mol.

Therefore, the mass of hydrogen formed when the change in heat is +90.7 KJ/mol would be:
Mass H2 = (x moles H2) * (2 g/mol)

Keep in mind that to provide an accurate answer, we need to know the "x" value, which is obtained by solving the equation using the actual value of the change in heat.