Calculate the standard enthalpy of reaction for the reaction 2 Na (s) + 2 H₂O (l)
2 NaOH (aq) + H₂ (g), Standard enthalpies
formation are -285.8 kJ/mol for H₂O and -470. 11 kJ/mol for NaOH (aq).

-368.62 kJ/mol

Explanation:

[(2 x - 470.11 kJ/mol) ( 0kJ/mol)] - [ 2 x -285.8 kJ/mol) (2x 0 kj/mol)] = -368.62 kJ/mol

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