Chemistry, 09.11.2019 21:31, bravooyessenia

Asolution of 20.0 g of which hydrated salt dissolved in 200 g h2o will have the lowest freezing point? (a) cuso4•5h2o(m=250)(b) niso4•6h2o(m=263)(c) mgso4•7h2o(m=246)(d) na2so4 • 10 h2o (m = 286)

Answers: 2

Show answers

Answers

answered: madbiebzz

The solution of Na₂SO₄ . 10H₂O ( choice D), will have the lowest freezing point.

Explanation:

1) The lowering of the freezing point is a colligative property which means that it depends, and can be calculated from some contants of the pure solvent, and the number of solute particles dissolved.

ΔTf = m × Kf × i

Where, ΔTf is the reduction in the freezing point, m is the molality of the solution, Kf is the cryoscopic constant of the solvent, and i is the Van't Hoff factor.

2) Find the molality of each solution, m:

Formulae:

moles of solute, n = mass in grams / molar mass

m = n / kg of solvent

(A) CuSO₄•5H₂O (M=250)

n = 20.0 g / 250 g/mol = 0.0800 molm = 0.0800 mol / 0.200 kg = 0.400 m

(B) NiSO₄•6H₂O(M=263)

n = 20.0 g / 263 g/mol = 0.0760 molm = 0.0760 mol / 0.200 kg = 0.380 m

n = 20.0 g / 246 g/mol = 0.0813 molm = 0.0813 mol / 0.200 kg = 0.406 m

(D) Na₂SO₄ • 10 H₂O (M = 286)

n = 20.0 g / 286 g/mol = 0.0699 molm = 0.0699 mol / 0.200 kg = 0.350 m

3) Van't Hoff factor.

Since, all the solutes are ionic, you start assuming that they all dissociate 100%.

That means that:

Each unit of CuSO₄.5H₂O yields 2 ions in water ⇒ i = 2Each unit of NiSO₄. 6H₂O yileds 2 ions in water ⇒ i = 2Each unit of MgSO₄.7H₂O yields 2 ions in water ⇒ i = 2Each unit of Na₂SO₄.10H₂O yields 3 ions in water ⇒ i = 3

4) Comparison

Being Kf a constant for the four solutions (same solvent), you just must compare the product m × i

CuSO₄.5H₂O: 2 × 0.400 = 0.800NiSO₄. 6H₂O: 2 × 0.380 = 0.760MgSO₄.7H₂O: 2 × 0.406 = 0.812Na₂SO₄.10H₂O: 3 × 0.406 = 1.218

As you see from above calculations, the dissociation factor defines the situation, and you can conclude that the last choice, i.e. the solution of Na₂SO₄ . 10H₂O, will have the greatest decrease of the freezing point, resulting in the lowest freezing point.

answered: Guest

shield volcanos are angry and get mad over the smallest things so much that there heads erupt pahoehoe and a'a lava. a composite volcano is the poller opposite of a shield volcano. its peaceful thing and knows how to control its emotions.

answered: Guest

False, as a substance changes from a solid to a liquid and from a liquid to a gas the molecules get farther apart from each other

Other questions on the subject: Chemistry

Chemistry, 22.06.2019 04:00, eborkins

Seltzer water is created by placing water under pressure with carbon dioxide gas. which of the following statements best describe seltzer water: a. the solution will be slightly acidic b. the solution will be slightly basic. the solution will be strongly acidic. d. the solution will be strongly basic. e. the solution will be neutral

Answers: 3

continue

Chemistry, 22.06.2019 12:30, gonzalesalexiaouv1bg

The missing component to the table to the right or indicated with orange letters complete the table by filling in the corresponding numbers or symbols

Answers: 3

continue

Chemistry, 22.06.2019 20:30, kittybatch345

Is a chemical message sent by another individual.

Answers: 1

continue

Chemistry, 22.06.2019 22:30, eduardoguizar8787

Which one of the following bonds would you expect to be the most polar? a) b–h b) n–h c) p–h d) al–h e) c–h

Answers: 1

continue

Do you know the correct answer?

Asolution of 20.0 g of which hydrated salt dissolved in 200 g h2o will have the lowest freezing poin...