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fenix001 [56]
3 years ago
7

Paradichlorobenzene, C6H4Cl2, is a component of mothballs. A solution of 2.00 g in 22.5 g of cyclohexane boils at 82.39 ∘C. The

boiling point of pure cyclohexane is 80.70 ∘C. Calculate Kb for cyclohexane. Express the constant numerically in degrees Celsius per molal.
Chemistry
1 answer:
Rina8888 [55]3 years ago
4 0

Answer:

2.79 °C/m

Explanation:

When a nonvolatile solute is dissolved in a pure solvent, the boiling point of the solvent increases. This property is called ebullioscopy. The temperature change (ΔT) can be calculated by:

ΔT = Kb*W*i

Where Kb is the ebullioscopy constant for the solvent, W is the molality and i is the van't Hoff factor.

W = m1/(M1*m2)

Where m1 is the mass of the solute (in g), M1 is the molar mass of the solute, and m2 is the mass of the solvent (in kg).

The van't Hoff factor represents the dissociation of the elements. For an organic molecule, we can approximate i = 1. Thus:

m1 = 2.00 g

M1 = 147 g/mol

m2 = 0.0225 kg

W = 2/(147*0.0225)

W = 0.6047 mol/kg

(82.39 - 80.70) = Kb*0.6047*1

0.6047Kb = 1.69

Kb = 2.79 °C/m

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Aleks04 [339]

Answer:

The number of formula units in 3.81 g of potassium chloride (KCl) is approximately 3.08 × 10²²

Explanation:

The given parameters is as follows;

The mass of potassium chloride produced in the chemical reaction (KCl) = 3.81 g

The required information = The number of formula units of potassium chloride (KCl)

The Molar Mass of KCl = 74.5513 g/mol

The \ number \ of \ moles \ of \ a \ substance, n = \dfrac{The  \  mass  \  of  \  the substance}{The   \  Molar  \   Mass   \  of  \   the   \  substance}

Therefore, we have;

The \ number \ of \ moles \ of \ KCl= \dfrac{3.81 \ g}{74.5513 \ g/mol} \approx 0.051106 \ moles

1 mole of a substance, contains Avogadro's number (6.022 × 10²³) of  formula units

Therefore;

0.051106 moles of KCl contains 0.051106 × 6.022 × 10²³  ≈ 3.077588 × 10²² formula units

From which we have, the number of formula units in 3.81 g of potassium chloride (KCl) ≈ 3.08 × 10²² formula units.

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3 years ago
Combustion of coal releases sulfur dioxide into the atmosphere. The following process converts this gas into sulfuric acid, a co
Usimov [2.4K]

Answer:

m=7.07gH_{2}SO_{4}

Explanation:

1. Take in account the sulfuric acid at STP:

1840\frac{g}{L}

2. Density is expressed as the ratio between the mass and the volume of a substance so:

d=\frac{m}{V}

Solving for m:

m=\frac{V}{d}

3. Replace values:

m=\frac{1.30*10^{4}L}{1840\frac{g}{L}}

m=7.07gH_{2}SO_{4}

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