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MissTica
3 years ago
13

The free energy change for the following reaction at 25 °C, when [Cr3+] = 1.32×10-3 M and [Fe3+] = 1.14 M, is 131 kJ: Cr3+(1.32×

10-3 M) + Fe2+(aq) Cr2+(aq) + Fe3+(1.14 M) ΔG = 131 kJ What is the cell potential for the reaction as written under these conditions? Answer: V Would this reaction be spontaneous in the forward or the reverse direction?
Chemistry
1 answer:
larisa [96]3 years ago
6 0

Answer:

E°cell = - 1.3575 V

This reaction is spontaneous in the reverse direction

Explanation:

The given cell reaction:

Cr³⁺(1.32 × 10⁻³ M) + Fe²⁺(aq) → Cr²⁺(aq) + Fe³⁺(1.14 M)

The given Gibbs free energy: ΔG = 131 kJ = 131 × 10³ J     (∵ 1 kJ = 10³ J)

As we know,

ΔG = - n F E°cell

Here, n - the number of moles of electrons transferred = 1

F - Faraday constant = 96500

E°cell - cell potential = ?

\therefore E^{\circ }_{cell} = -\frac{\Delta G}{n \: F} = -\frac{131\times 10^{3}\, J}{1\, mol\times96500 \, C.mol^{-1}}

\Rightarrow E^{\circ }_{cell} = -1.3575\, V

<u>For a given chemical reaction if-</u>

1. ΔG = negative and E°cell = positive

⇒ <em>The reaction is spontaneous and proceeds spontaneously in the forward direction.</em>

2.  ΔG = positive and E°cell = negative

⇒ <em>The reaction is non-spontaneous and proceeds spontaneously in the reverse direction.</em>

<u>Since, for this chemical reaction: </u>

Cr³⁺(1.32 × 10⁻³ M) + Fe²⁺(aq) → Cr²⁺(aq) + Fe³⁺(1.14 M)

ΔG = + 131 × 10³ J ⇒ positive

and, E°cell = - 1.3575 V ⇒ negative

<u>Therefore, this reaction is spontaneous in the reverse direction.</u>

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A sample of pure NH4HS is placed in a sealed 2.0-L container and heated to 550 K at which the equilibrium constant is 3.5 x 10-3
Zolol [24]

Answer:

The mass of NH_{3} in the container is 2.074 gram

Explanation:

Given:

Volume of NH_{4} HS    V = 2 lit

Equilibrium constant k _{eq} = 3.5 \times 10^{-3}

The reaction in which NH_{3} is produced

  NH_{4} HS ⇄ NH_{3} + H_{2}S

Here equal moles of NH_{3} and H_{2}S is formed.

From the formula of equilibrium constant,

  k_{eq} = (NH_{3})(H_{2}S )

   x^{2} = 3.5 \times 10^{-3}

     x = 0.061 M

Above value shows,

   NH_{3} = 0.061 \frac{moles}{L}

So in 2 L no. moles of NH_{3} = 0.061 \times 2 = 0.122 moles.

So mass of 0.122 mole of NH_{3} is = 0.122 \times 17 = 2.074 g

Therefore, the mass of NH_{3} in the container is 2.074 gram

8 0
3 years ago
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Igoryamba

Answer:

The arm that was not sprayed with anything

Explanation:

The control group would be <u>the arm that was not sprayed with anything</u>.

<em>The control group during an experiment is a group that forms the baseline for comparison in other to determine the effects of a treatment. The control group does not include the variable that is being tested and as such, it provides the benchmark to measure the effects of the tested variable on the other group - the experimental group. In this case, the experimental group would be the arm that was sprayed with the repellent.</em>

8 0
2 years ago
What do you get when you mix lemons with gunpowder
Nezavi [6.7K]
The answer is Lemonades
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3 years ago
At 63.5 C the vapor pressure of H2O is 175 torr and that of ethanol is 400 torr. A solution is made by adding equal masses of H2
xxTIMURxx [149]

Answer:

Moel fraction of ethanol in the solution = 0.28

Vapor pressure of the solution = 238 torr

Mole fraction of ethanol in the vapor = 0.47

Explanation:

Let's use 100 g of each substance as a calculus basis. Knowing that the molar mass of water is 18 g/mol and the molar mass of ethanol is 46 g/mol, the number of moles (n = mass/molar mass) of each one is:

nw = 100/18 = 5.56 mol

ne= 100/46 = 2.17 mol

The total number of moles is 7.73 mol, so the mole fraction of ethanol is

2.17/7.73 = 0.28

The mole fraction of water must be 0.72, so if we assume that the solution is ideal, by the Raoult's law, the solution vapor pressure is the sum of the multiplication of the mole fraction by the vapor pressure of each substance, thus:

P = 0.28*400 + 0.72*175

P = 238 torr

The partial pressure of each substance can be found by the multiplication of the molar fraction by the vapor pressure, thus:

Pw = 0.72*175 = 126 torr

Pe = 0.28*400 = 112 torr

To know the number of moles that is vaporized above the solution, we may use the ideal gas law:

PV = nRT

P/n = RT/V

R is the gas constant, T is the temperature and V is the volume, so they are the same for both water and ethanol, thus

Pw/nw = Pe/ne

126/nw = 112/ne

ne = (112/126)*nw

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So, the mole fraction of ethanol is:

ne/(ne + nw) = 0.89nw/(0.89nw + nw) = 0.89/1.89 = 0.47

4 0
3 years ago
What is the percent of oxygen by mass in a pure sample of fecr2o4? 1. 52% 2. 13% 3. 37% 4. 7.1% 5. 29%?
Marta_Voda [28]
Let us suppose that we have 1 mol of FeCr2O4. I'm going to use approximate masses because I have no idea what your periodic table will say. Just put in the exact masses from your periodic table.

Fe = 56
Cr*2 = 2*52 = 104
O4 = 4*16 = 64
===========
Total = 56 + 104 + 64 = 224
The % oxygen = (64 / 224) * 100 = 28.5 % but none of your answers match this. Perhaps you are talking about Fe2(Cr2O4)3 The brackets make all the difference in the world.

Without going through all the detail I did before, The molecular mass is
Fe * 2 = 112
Cr * 6 = 312
O * 12 = 192
The total molecular mass = 616

The % Oxygen = (192 / 616) * 100 = 31% roughly. That answer isn't there either. 

Let's wait and see who else answers.

6 0
3 years ago
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