brunetteangel

I know. I get the right solution when I multiply the standard enthalpy by 4, so my proportion looks like this: 123,89g... -66,92kJ 1.000.000g ... x Then x turns out to be 540156,5905 kJ, and that is the right solution, but I don't know how to explain why I multiplied the standard enthalpy. I know that red phosphorus has chain structure, and that the chain can consist of n phosphorus atoms, and that's why it's formula is Pn. But in this reaction, I have P4 (so that's 4 phosphorus atoms) turning into Pn, red phosphorus. Does that mean that the chain of red phosphorus has to consist of 4 atoms of phosphorus, too?

The problem is this: Calculate how much heat is being released in the reaction of white phosphorus turning into red phosphorus if the mass of white phosphorus is 1000 kg. Standard enthalphy of this reaction is -16,73 kJ/mol. Now, I tried solving it using proportion, like this: P4 -> Pn 123,89g ... -16,73kJ 1.000.000g ... x But when I calculate x, I get 135.033,6543 kJ, and the solution at the back of the book is different, it's 5,4 * 10^5 kJ. Can someone please tell me where I made mistakes? Thanks.

I think I got it, thanks to your questions. 1) in 89,6 cubic dm of ammonia there are 4 nitrogen atoms =>in 1.000.000 cubic dm of ammonia there are 44.642,85714 nitrogen atoms 2) 1 mol of nitric acid contains 1 nitrogen atom =>44.642,85714 mol of nitric acid contains 44.642,85714 nitrogen atoms 3) 1 mol of nitric acid weighs 63,0128 g =>44.642,85714 mol of nitric acid weigh 2.813.071,428 g, that is, 2.813 kg Thanks to both of you for helping.

Oh thanks. But I tried counting the nitrogen atoms again, but the solution always comes out to be 1406,53 kg. :/ And should I use all 3 formulas or just the proportion?

So, here's my problem. Calculate how much HNO3 you can get (theoretically) from 1000 cubic meters of NH3. Now, the only way of getting HNO3 using NH3 is this one: 4NH3 + 5O2 -> 4NO + 6H20 2NO + O2 -> 2NO2 3NO2 + H2O -> 2HNO3 + NO So I thought I could do it this way: from 4NH3 I get -> 2 HNO3 so, from 89,6 cubic dm of NH3 I get -> 126,0256g of HNO3 then, from 1.000.000 cubic dm of NH3 I will get -> x (unknown mass) of HNO3 But the problem is, I get the wrong result when I calculate it. I get 1.406, 53 kg and the solution at the end of the book says 2.812,5 kg. Please tell me where I made mistakes. Thanks.