A compound A reacts according to the following hypothetical equation and has a molecular weight of 48.36 g/mol.
3 A (s) +B (aq) ––> 2 C (aq) ∆H° = ?
A sample of A, weighing 0.152 g reacts in a flask containing 250.00 g of water and the water temperature increases from 24.85 °C to a temperature of 26.26 °C. Calculate ∆H° for the reaction as written in the equation.
Answer: -1408 kJ
For which of the following reactions is ∆H° = ∆H°f, the heat of formation?
i. C (s) + 2 F2(g) ––> CF4 (g) ∆H° = – 221.0 kJ ii. H(g) + Br (g) ––> HBr (g) ∆H° = –366.2 kJ iii. 2 C(s) + H2(g) + 3 Cl2(g) ––> 2 CHCl3 (g) ∆H° = –268.2
Answer: i only
Also, could someone explain exactly what delta H means in terms of Thermochemistry. I would like to have a better understanding of it.
Thank you very much! :)
For the first question I attempted to use the q=m x s x (delta) T for the water and I attempted to use stochiometry for substance A but I always receive the wrong answer. Could someone help me on where to start with these types of problems?
(250) x (4.184) x (26.26-24.85)
= 1474.86 kJ