Use the standard heats of formation provided to choose the choice that show the valid math statement and math claim to calculate the standard heat of reaction for the reaction between hydrogen gas and oxygen gas shown. 2H2 (g) + O2 (g) → 2H2O (l)

Substance ΔH°f (kJ/mol)
H2 (g) 0
O2 (g) 0
H20 (l) -285.8
A)(0-0) - (-285) = 285 kJ/mol
B)0 - (-285-0) = -285 kJ/mol
C)-285 - (0-0) = -285 kJ/mol
D)(-285-0) - (0) = 285 kJ/mol

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%

un recipient conține 6,4 moli de gaz. gazul hidrogen reprezintă 25% din totalul kilometrilor din container. în cazul în care presiunea totală este de 1.24 atm ceea ce este