This is a question about the colligative property known as freezing point depression. Freezing point depression (the amount the normal freezing point of the solvent is decreased) can be calculated with this equation:
ΔT = i Kf<span> m
</span>
Where i (the van't Hoff factor) is the degree of dissociation of the solute, Kf is the freezing point depression constant, and m is the molality of the solution.
Here i = 2 (KCl dissociates into 2 ions, K+ and Cl-), Kf = 1.86 C/m (for water), and m = 0.743m).
ΔT = 2 x 1.86 C/m x 0.743m = <span>2.764C
</span>
That means the freezing point of the solution is 2.764C less than the pure solvent (water), making it 0C - 2.764C = -2.764C.
Answer:
1) Exothermic.
2)
3)
Explanation:
Hello there!
1) In this case, for these calorimetry problems, we can realize that since the temperature increases the reaction is exothermic because it is releasing heat to solution, that is why the temperature goes from 22.0 °C to 28.6 °C.
2) Now, for the total heat released by the reaction, we first need to assume that all of it is absorbed by the solution since it is possible to assume that the calorimeter is perfectly isolated. In such a way, it is also valid to assume that the specific heat of the solution is 4.184 J/(g°C) as it is mostly water, therefore, the heat released by the reaction is:
3) Finally, since the enthalpy of reaction is calculated by dividing the heat released by the reaction over the moles of the solute, in this case LiCl, we proceed as follows:
Best regards!
D. The air pressure increases
Answer:
0.1738 M
Explanation:
Let's consider the neutralization reaction between NaOH and HBr.
NaOH + HBr → NaBr + H₂O
The moles of HBr are:
14.76 × 10⁻³ L × 0.4122 mol/L = 6.084 × 10⁻³ mol
The molar ratio of NaOH to HBr is 1:1. In the endpoint, they have reacted completely, so the moles of NaOH were 6.084 × 10⁻³ mol before the reaction.
The molarity of NaOH is:
M = 6.084 × 10⁻³ mol / 35.00 × 10⁻³ L = 0.1738 M
They have different neutron number and thus different mass number, but they are the same element.