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Thepotemich [5.8K]
3 years ago
9

Ashmita pours 425 mL of Methanol into an insulated cup. (The density of Methanol is 0.792 g/mL, and the specific heat of liquid

Methanol is 2.597 J/g/deg C.) She measures the initial temperature to be 18.0 deg C. She puts the cup of Methanol into her freezer for 1.50 hours. When she pulls it out of the freezer, she measures the temperature to be -5.0 deg C. Calculate the amount of heat energy Q removed from the liquid Methanol.
Chemistry
1 answer:
Marina CMI [18]3 years ago
5 0

Answer:

Mol. mass of ethyl alcohol =C2H5OH=46

No. of moles of ethyl alcohol =4660=1.304

Mol. mass of methyl alcohol =CH3OH=32

No. of moles of methyl alcohol =3240=1.25

′XA′, mole fraction of ethyl alcohol =1.304+1.251.304=0.5107

′XB′, mole fraction of methyl alcohol =1.304+1.251.25=0.4893

Partial pressure ethyl alcohol =XAp˙A0=0.5107×44.5=22.73mmHg

Partial pressure methyl alcohol =XBp˙B0=0.4893×88.7=73.40mmHg

Total vapour pressure of solution =22.73+43.40=66.13mmHg

Mole fraction of methyl alcohol in the vapour

=Total vapour pressurePartial pressure of CH3OH

Explanation:

I HOPE THIS HELPS YOU

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Phosphine, PH₃, is a colorless, toxic gas that is used in the production of semiconductors as well as in the farming industry. W
Vilka [71]

Answer:

0.57 atm

Explanation:

Anytime a reaction is of the first order, the integrated law states that

ln[A]t/[A]₀ = - kt

where [A]t is the concentration of A ( phosphine in this question ) after a time, t

          [A]₀ is the initial concentration of A (phosphine also)

          k is a constant,

          t is the time

We also know that for a first order reaction,

          half life is t1/2 =0.693/k, then, k= 0.693/ t 1/2

where t 1/2 is the half-life.

This equation is derived for a situation when A]t/= 1/2 x [A]₀ which occurs at the half-life.

Thus, finding k from the half life time, and then solving it for a time t = 70.5 s

k = 0.693 /  35.0 s = 0.0198 s⁻¹

ln [ PH₃ ]t / [ PH₃]₀ = - kt

from ideal gas law we know that pV = nRT, so the volumes  will cancel:

ln (pPH₃ )t / p(PH₃)₀ = - kt

taking inverse log to both sides of the equation:

(pPH₃ )t / p(PH₃)₀  = - kt

then

(pPH₃ )t  = 2.29 atm x e^(- 0.0198 s⁻¹ x 70.5 s ) = 0.57 atm

4 0
2 years ago
If 0.896 g of a gas occupies a 250 mL flask at 20°C and 760 mm Hg of pressure, what is the molar mass of the gas?​
salantis [7]

Answer:

86.2 g/mol

Explanation:

Before you can find the molar mass, you first need to calculate the number of moles of the gas. To find this value, you need to use the Ideal Gas Law:

PV = nRT

In this equation,

-----> P = pressure (mmHg)

-----> V = volume (L)

-----> n = moles

-----> R = Ideal Gas constant (62.36 L*mmHg/mol*K)

-----> T = temperature (K)

After you convert the volume from mL to L and the temperature from Celsius to Kelvin, you can use the equation to find the moles.

P = 760 mmHg                                      R = 62.36 L*mmHg/mol*K

V = 250 mL / 1,000 = 0.250 L              T = 20 °C + 273.15 = 293.15 K

n = ? moles

PV = nRT

(760 mmHg)(0.250 L) = n(62.36 L*mmHg/mol*K)(293.15 K)

190 = n(18280.834)

0.0104 = n

The molar mass represents the mass (g) of the gas per every 1 mole. Since you have been given a mass and mole value, you can set up a proportion to determine the molar mass.

\frac{?grams}{1 mole} =\frac{0.896grams}{0.0104moles}                                      <----- Proportion

?grams(0.0104moles) = 0.896                       <----- Cross-multiply

?grams = 86.2                                               <----- Divide both sides by 0.0104

8 0
1 year ago
Which phase change in an example of an exothermic process?
photoshop1234 [79]
C. liquid to solid  i hope this helps

5 0
3 years ago
Read 2 more answers
1. a.) Calculate the wavelength of light which has a frequency of 5.25 x 10 14 Hz.
Scilla [17]
<h3>Answer:</h3>

5.71 × 10² nm

<h3>Explanation:</h3>

The product of wavelength and frequency of a wave gives the speed of the wave.

Therefore;

Velocity of wave = Wavelength × Frequency

c = f ×λ

In our case;

Frequency = 5.25 × 10^14 Hz

Speed of light = 2.998 × 10^8m/s

But;

λ = c ÷ f

  = 2.998 × 10^8m/s ÷  5.25 × 10^14 Hz

  = 5.71 × 10^-7 m

But; 1 M = 10^9 nm

Therefore;

wavelength = 5.71 × 10^-7 × 10^9

                  = 5.71 × 10² nm

The wavelength of light wave 5.71 × 10² nm

3 0
3 years ago
In a _________the molecules are very close together
Maurinko [17]
Is a solid because liquids are not is not that close and gas is very far apart.
4 0
3 years ago
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