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Vladimir79 [104]
3 years ago
11

At 55.0 ∘C, what is the vapor pressure of a solution prepared by dissolving 78.4 g of LiF in 253 g of water? The vapor pressure

of water at 55.0 ∘C is 118 mmHg. Assume complete dissociation of the solute. Express your answer to three significant figures and include the appropriate units.
Chemistry
1 answer:
ddd [48]3 years ago
7 0

Answer:

82.5 mmHg

Explanation:

The vapor pressure of a solution that contains a non-volatile solute will depend on the mole fraction of the solvent and on the vapor pressure of the pure solvent at the same temperature.

P sol=  χsolvent ⋅ P∘solvent, where

Psol - the vapor pressure of the solution

χ solvent - the mole fraction of the solvent

P ∘solvent - the vapor pressure of the pure solvent

Now, the most important thing to realize here is that lithium fluoride,  

LiF , a soluble ionic compound, will dissociate completely in aqueous solution to form lithium cations and fluoride anions.

LiF (aq] → Li+(aq]  + F − (aq]

Notice that every mole of lithium fluoride produces one mole of lithium cations and one mole of fluoride anions.

This means that you get a total of two moles of ions for every one mole of lithium fluoride in the solution.

Use lithium fluoride's molar mass to determine how many moles would be found in the given sample

78.4g⋅ (1 mole LiF /25.94 g)  = 3.022 moles LiF

This means that the solution will contain

3.022 moles LiF ⋅  (2 moles ions /1 mole LiF)  = 6.044 moles ions

Now, water's mole fraction in this solution will be equal to the number of moles of water divided by the total number of moles present in the solution.

To get the number of moles of water, use its molar mass

253  g  ⋅  (1 mole H 2O / 18.015 g) = 14.044 moles H 2O

This means that water's mole fraction will be

χwater = 14.044 moles  / (14.044 +6.044 )moles = 0.6991

The vapor pressure of the solution will thus be

Psol= 0.6991  ⋅ 118 mmHg = 82.5 mmHg

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natima [27]

Answer:

A) 6.00 mol.

B) 0.375 L or 375 mL

C) 6.00 M

Explanation:

Hello,

A) In this case, from the definition of molarity, we compute the moles for the given volume and concentration:

n=M*V=1.00L*6.00mol/L=6.00mol

B) In this case, from the stock solution, the required volume is:

V=\frac{6.00mol}{16.00mol/L}=0.375L

C) In this case, we apply the following formula for dilution process:

M_1V_1=M_2V_2

Thus, solving for the final molarity, we obtain:

M_2=\frac{M_1V_1}{V_2}=\frac{16.00M*0.375L}{1.00L}\\  \\M_2=6.00M

Regards.

5 0
2 years ago
Given that the frequency of a wave is 9.12x10^-12 Hz, what must be the
polet [3.4K]

Answer:

The wavelength of wave is 0.33 ×10²⁰ m.

Explanation:

Given data:

Frequency of wave = 9.12×10⁻¹² Hz

Wavelength of wave = ?

Solution:

Formula:

Speed of light = wavelength × frequency

c = λ × f

λ = c/f

This formula shows that both are inversely related to each other.

The speed of light is 3×10⁸ m/s

Frequency is taken in Hz.

It is the number of oscillations, wave of light make in one second.

Wavelength is designated as "λ" and it is the measured in meter. It is the distance between the two crust of two trough.

Now we will put the values in formula.

λ = 3×10⁸ m/s  / 9.12×10⁻¹² Hz

Hz = s⁻¹

λ = 0.33 ×10²⁰ m  

The wavelength of radiation is 0.33 ×10²⁰ m  .

5 0
3 years ago
What did J. J. Thomson observe when he applied electric voltage to a cathode ray tube in his famous experiment?
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The glass opposite to the negative electrode started to glow. Hence, option B is correct.

<h3>What is a cathode ray tube?</h3>

A cathode-ray tube (CRT) is a specialized vacuum tube in which images are produced when an electron beam strikes a phosphorescent surface.

J.J. Thomson, through his famous Cathode ray experiment, proved that all atoms contain small negatively charged particles known as electrons. In the experiment, he applied electric voltage across a cathode ray tube. a fluorescent material coating was done on the positive side. When the voltage was applied, the positive side has glowing dots.

Hence, option B is correct.

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6 0
1 year ago
Nitrogen and water react to form nitrogen monoxide and hydrogen, like this: N2(g) + 2H2O(g) → 2NO(g) +2H2(g) Also, a chemist fin
Thepotemich [5.8K]

Answer:

Kc for this reaction is 0.43

Explanation:

This is the equilibrium:

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And we have all the concentration at equilibrium:

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They are ok, because they are in MOLARITY. (mol/L)

Let's make the expression for Kc

Kc = ( [NO]² . [H₂]² ) / ([N₂] . [H₂O]²)

Kc = (0.33² . 1.2²) / (0.25 . 1.2²)

Kc = 0.4356

In two significant digits. 0.43

8 0
3 years ago
What devices will you use to measure the mass and the volume in this experiment? (density)
bekas [8.4K]

Answer:

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Explanation:

8 0
2 years ago
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