Answer:
ΔH°f(C₈H₁₈(g)) = -210.9 kJ/mol
Explanation:
Let's consider the combustion of C₈H₁₈.
C₈H₁₈(g) + 25/2 O₂(g) ⟶ 8 CO₂(g) + 9 H₂O(g) ΔH°rxn = − 5113.3 kJ
We can calculate the standard enthalpy of formation of C₈H₁₈(g) using the following expression.
ΔH°rxn = 8 mol × ΔH°f(CO₂(g)) + 9 mol × ΔH°f(H₂O(g)) - 1 mol × ΔH°f(C₈H₁₈(g)) - 25/2 mol × ΔH°f(O₂(g))
1 mol × ΔH°f(C₈H₁₈(g)) = 8 mol × ΔH°f(CO₂(g)) + 9 mol × ΔH°f(H₂O(g)) - 25/2 mol × ΔH°f(O₂(g)) - ΔH°rxn
1 mol × ΔH°f(C₈H₁₈(g)) = 8 mol × (-393.5 kJ/mol) + 9 mol × (-241.8 kJ/mol) - 25/2 mol × 0 kJ/mol - (− 5113.3 kJ)
ΔH°f(C₈H₁₈(g)) = -210.9 kJ/mol
You have molarity and you have volume. Use the formula :
Molarity(M)= Moles(N)/Liter(L) to get the solution.
450 ml= .450 L
.250 = N/.450
N=.1125 moles of NaOH.
And since you know the moles, use the molar mass to figure out the grams.
<span> (40g/mol NaOH) x (.1125 mol) =
4.5g of NaOH.
</span>
Hope it helps. Good luck on chemistry.
Answer:
a) 200 L of water. b) 3,2210(fifth to the power) kg
Explanation:
a) To reach toxic level of a person would have to drink 200 L of water. b) We need 3,2210 to the fifth power kg of fluride for 8,510 to the seventh power gal of water.
This equation shows how HF, hydrofluoric acid behaves in water.
HF (aq) ----> H+ (aq) + F- (aq). In water acids will dissociate into positive cations and negative anions. The strength or weakness of an acid depends on its ability to dissociate in water. Substances that dissociate completely are strong acids while partial dissociation indicates a weak acid. HF is considered to be a weak acid because it does not completely dissociates in water. There is instead an equilibrium between HF molecules and the dissociates.