In the reaction, 210 kJ of heat energy is used to form 3.0 moles of hydrogen. Calculate how much heat energy is needed to make 1000 kg of hydrogen.

Heat energy needed : 3.5 x 10⁷ kJ

Heat is a form of energy that can flow from high-temperature objects to low-temperature objects.

So heat moves when there is a difference in temperature and can increase or decrease the temperature. An object that receives a lot of heat will cause a large increase in temperature

The amount of heat is influenced by the mass of the object and the difference in temperature

Can be formulated

Q = m.c.Δt

Q: heat received or removed by an object (J)

m: object mass (kg)

c: heat type substance (J / kg⁰C)

ΔT: temperature change (⁰C)

210 kJ of heat energy is used to form 3.0 moles of Hydrogen, so heat energy for 1 mol Hydrogen :

mol of 1000 kg of Hydrogen=10⁶ g(MW=2 g/mol)

The heat energy :

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.