PLZ HELP For the reaction: 2NO2(g) → N2O4(l), the ΔH of the reactants, two moles of NO2 (g), is + 66 kJ/mol,
and the ΔH of the products, N2O4 (l), is -20 kJ/mol.
Which of the following shows the ΔH (change in enthalpy) for the reaction as a whole?

Question 8 options:

ΔrxnH =(- 20 kJ/mol) / (+66 kJ/mol)

ΔrxnH = (+66 kJ/mol) + (- 20 kJ/mol)

ΔrxnH =(-20 kJ/mol) - (+ 66 kJ/mol)

ΔrxnH =(+66 kJ/mol) - (- 20 kJ/mol)

Explanation:

Heat of reaction or enthalpy change is the energy released or absorbed during the course of the reaction.

It is calculated by subtracting the enthalpy of reactants from the enthalpy of products.

= enthalpy change = ?

= enthalpy of products

= enthalpy of reactants

For the given reaction :

1. 1 mole of anything contains 6.022x10^23 pieces  

d  

2. a  

3. c, number  

5. 1.24x10^24atoms / 6.022x10^23atoms/mole = 2moles h2 atoms  

6. fe2br3 mass = 2moles x mass fe + 3 moles x mass br  

molar mass = grams / number of moles = g/mole  

to find moles = g / molar mass  

to find mass = g = molar mass / moles