Given the following information:

2NaHCO3(s) + 85 kJ → Na2CO3(s) + H2O(l) CO2(g)
Calculate the amount of heat (in kJ) required to decompose 2.24 mol NaHCO3(s). You must show your work to receive credit.

I need serious help with this.

4 answers

You're looking at the trees. You should be looking at the forest.
The equation tells you 2 mols NaHCO3 requires 85 kJ heat. So you want 2.24.

If I asked you how much heat to do just 1 mol you would say immediately
85/2 kJ wouldn't you? If I asked how much heat to decompose not 2 but 4 mol you would say immediately 85 x 2 = ? wouldn't you. How did you get those two numbers? Easy. For the first one you said
85 x (1/2) = 85 x (what I want/what equation has) = ? For second one you said
85 x 4/2 = 85 x (what I want/what equation has) = ?
So why wouldn't you do this one by 85 x 2.24/2 = ?

You know 2 mols uses 85 kJ so that is 85/2 = 42.5 kJ/mol and you want 2.24 mols so 42.5 kJ/mol x 2.24 mols = ?. Note that by doing this you cancel mols and the answer is in kJ which is what you want. You would be surprised at how many problems can be worked this way.

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