Answer:
-238.54 kJ/mol.
Explanation:
- We need to calculate the standard enthalpy of formation of liquid methanol, CH₃OH(l) that has the equation:
C(graphite) + 2H₂(g) + ½ O₂(g) → CH3OH(l) ΔHf° = ?
?? kJ/mol.
- using the information of the three equations:
(1) C(graphite) + O₂(g) → CO₂(g), ΔHf₁° = -393.5 kJ/mol
.
(2) H2(g) + ½ O₂(g) → H₂O(l), ΔHf₂° = -285.8 kJ/mol
.
(3) CH₃OH(l) + 3/2 O₂(g) → CO₂(g) + 2H₂O(l), ΔH₃° = -726.56 kJ/mol
.
- We rearranging and add equations (1, 2, and 3) in such a way as to end up with the needed equation:
- equation (1) be as it is:
(1) C(graphite) + O₂(g) → CO₂(g), ΔHf₁° = -393.5 kJ/mol
.
- equation (2) should be multiplied by (2) and also the value of ΔHf₂°:
(2) 2H2(g) + O₂(g) → 2H₂O(l), ΔHf₂° = 2x(-285.8 kJ/mol
).
- equation (3) should be reversed and also the value of ΔH₃° should be multiplied by (-1):
(3) CO₂(g) + 2H₂O(l) → CH₃OH(l) + 3/2 O₂(g), ΔH₃° = 726.56 kJ/mol
.
- By summing the modified equations, we can get the needed equation and so:
The standard enthalpy of formation of liquid methanol, CH₃OH(l) = ΔHf₁° + 2(ΔHf₂°) - ΔH₃° = (-393.5 kJ/mol
) + 2(-285.8 kJ/mol
) - (- 726.56 kJ/mol) = -238.54 kJ/mol.
Answer:
80.8 g
Explanation:
First, let's write a balanced equation of this reaction
MgO + 2HNO₃ → Mg(NO₃)₂ + H₂O
Now let's convert grams to moles
We gotta find the weight of MgO
24 + 16 = 40 g/mol
12/40 = 0.3 moles of MgO
We can use this to find out how much Magnesium Nitrate will be formed
0.3 x 1 MgO / 1 Mg(NO₃)₂ = 0.3 moles of Magnesium Nitrate formed
Convert moles to grams
Find the weight of Mg(NO₃)₂ but don't forget that 2 subscript acts as a multiplier of whatever is inside that parenthesis.
24 + 14 x 2 + 16 x 3 x 2 = 148 g/mol
148 x 0.3 = 80.8 g
Answer:
Option A
Explanation:
Addition of too much of solvent will make the solution dilute due to which the crystals will not form. Hence option D is incorrect
On the other hand adding a minimum amount of boiling solvent will give a saturated solution for recrystallization. Hence, option A is incorrect
Addition of cold solvent will lower the rate of formation of crystals. Hence, both option B and C are incorrect
<span>Colligative properties are properties of solutions that depend on the number of molecules [or ions] in a given volume of solvent and not on the properties (e.g. size or mass) of the compound. Colligative properties include: lowering of vapor pressure; elevation of boiling point; depression of freezing point and osmotic pressure.</span>