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Otrada [13]
3 years ago
6

A voltaic cell consists of a Zn/Zn2+ half-cell and a Ni/Ni2+ half-cell at 25 ?C. The initial concentrations of Ni2+ and Zn2+ are

1.70M and 0.130M , respectively. The volume of half-cells is the same.Part AWhat is the initial cell potential?Express your answer using two significant figures.Part BWhat is the cell potential when the concentration of Ni2+ has fallen to 0.500M ?Express your answer using two significant figures.Part CWhat is the concentrations of Ni2+ when the cell potential falls to 0.45V ?Express your answer using one significant figure.Part DWhat is the concentration of Zn2+ when the cell potential falls to 0.45V ?Express your answer using two significant figures.
Chemistry
1 answer:
inna [77]3 years ago
4 0

Answer:

a) E = 0.477 V

b) E = 0.502 V

c) 0.02 M = [Ni+2]

d)[Zn+2] = 1.81 M

Explanation:

having the following reactions of each cell:

Zn =⇒  Zn+2   +  2e-    +0.76

Ni+2  +  2e- =⇒   Ni       -0.25

Zn  +  Ni+2  ==⇒  Ni     +    Zn+2     Eo = 0.51

a)

The number of electrons being transferred is 2, therefore n = 2 in the Nernst equation

E =  Eo - 0.0592/2*log [Zn+2]/[Ni+2] = 0.51 - 0.0592/2*log[0.13/1.7] = 0.477 V

b)

using the formula above:

E = 0.51  - 0.0296*log [Zn+2]/[Ni+2] = 0.51 - 0.0296*log((0.13+0.5)/(1.7-0.5)) = 0.502 V

c)

using the formula above:

0.45 = 0.51  - 0.0296*log[Zn+2]/[Ni+2]

-0.06/-0.0296 = log[Zn+2]/[Ni+2]

2.02 = log [Zn+] / [Ni+2]

104.71 = [Zn+2] / [Ni+2]

x = change in [Ni+2]

[Ni+2]  = 1.70 -  x

[Zn+2] =  0.13 +  x

0.13 + x/1.70 –x =  104.71

Resolving  x:

x = 1.68 M

[Ni+2]  = 1.70 -  1.68 = 0.02 M

d)

[Zn+2] =  0.13 +  x = 0.13 + 1.68 = 1.81 M

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Goryan [66]

Answer:

Chemical indicator, any substance that gives a visible sign, usually by a color change, of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution. An example is the substance called methyl yellow, which imparts a yellow color to an alkaline solution.

7 0
2 years ago
One mole of an ideal gas, for which CV,m = 3/2R, initially at 298 K and 1.00 × 105 Pa undergoes a reversible adiabatic compressi
oksian1 [2.3K]

Answer:

  • final temperature (T2) = 748.66 K
  • ΔU = w = 5620.26 J
  • ΔH = 9367.047 J
  • q = 0

Explanation:

ideal gas:

  • PV = RTn

reversible adiabatic compression:

  • δU = δq + δw = CvδT

∴ q = 0

∴ w = - PδV

⇒ δU = δw

⇒ CvδT = - PδV

ideal gas:

⇒ PδV + VδP = RδT

⇒ PδV = RδT - VδP = - CvδT

⇒ RδT - RTn/PδP = - CvδT

⇒ (R + Cv,m)∫δT/T = R∫δP/P

⇒ [(R + Cv,m)/R] Ln (T2/T1) = Ln (P2/P1) = Ln (1 E6/1 E5) = 2.303

∴ (R + Cv,m)/R = (R + (3/2)R)/R = 5/2R/R = 2.5

⇒ Ln(T2/T1) = 2.303 / 2.5 = 0.9212

⇒ T2/T1 = 2.512

∴ T1 = 298 K

⇒ T2 = (298 K)×(2.512)

⇒ T2 = 748.66 K

⇒ ΔU = Cv,mΔT

⇒ ΔU = (3/2)R(748.66 - 298)

∴ R = 8.314 J/K.mol

⇒ ΔU = 5620.26 J

⇒ w = 5620.26 J

  • H = U + nRT

⇒ ΔH = ΔU + nRΔT

⇒ ΔH = 5620.26 J + (1 mol)(8.314 J/K.mol)(450.66 K)

⇒ ΔH = 5620.26 J + 3746.787 J

⇒ ΔH = 9367.047 J

8 0
3 years ago
A mixture containing nitrogen and hydrogen weighs 3.49 g and occupies a volume of 7.45 L at 305 K and 1.03 atm. Calculate the ma
-BARSIC- [3]

Answer:

Mass percent N₂ = 89%

Mass percent H₂ = 11%

Explanation:

First we <u>use PV=nRT to calculate n</u>, which is the total number of moles of nitrogen and hydrogen:

  • 1.03 atm * 7.45 L = n * 0.082 atm·L·mol⁻¹·K⁻¹ * 305 K
  • n = 0.307 mol

So now we know that

  • MolH₂ + MolN₂ = 0.307 mol

and

  • MolH₂ * 2 g/mol + MolN₂ * 28 g/mol = 3.49 g

So we have a <u>system of two equations and two unknowns</u>. We use algebra to solve it:

Express MolH₂ in terms of MolN₂:

  • MolH₂ + MolN₂ = 0.307 mol
  • MolH₂ = 0.307 - MolN₂

Replace that value in the second equation:

  • MolH₂ * 2 g/mol + MolN₂ * 28 g/mol = 3.49
  • (0.307-MolN₂) * 2 + MolN₂ * 28 = 3.49
  • 0.614 - 2MolN₂ + 28molN₂ = 3.49
  • 0.614 + 26MolN₂ = 3.49
  • MolN₂ = 0.111 mol

Now we calculate MolH₂:

  • MolH₂ + MolN₂ = 0.307 mol
  • MolH₂ + 0.111 = 0.307
  • MolH₂ = 0.196 mol

Finally, we convert each of those mol numbers to mass, to <u>calculate the mass percent</u>:

  • N₂ ⇒ 0.111 mol * 28 g/mol = 3.108 g N₂
  • H₂ ⇒ 0.196 mol * 2 g/mol = 0.392 g H₂

Mass % N₂ = 3.108/3.49 * 100% = 89.05% ≅ 89%

Mass % H₂ = 0.392/3.49 * 100% = 11.15% ≅ 11%

5 0
3 years ago
The recommended dose for acetaminophen is 10.0 to 15.0mg/kg of body weight for adults using this guideline calculate the maximum
Oxana [17]

Answer:

1422mg of acetaminophen

Explanation:

The maximum dose of acetaminophen is 15.0 mg of acetaminophen per kg of person.

To know the maximum single dosage of the person we need to convert the 209lb to kg (Using 1kg = 2.2046lb):

209lb * (1kg / 2.2046lb) = 94.8

The person weighs 94.8kg and the maximum single dosage for the person is:

94.8kg * (15.0mg acetaminophen / kg) =

1422mg of acetaminophen

4 0
2 years ago
What material is the source for commercial production of each of the following elements:(a) aluminum;
AleksandrR [38]

The material which is used as source for commercial production aluminum is bauxite.

The aluminum can be extracted from bauxite ore by the process of Bayer process.

In the Bayer process, bauxite ore is heated in the pressure vessel along with a caustic soda solution (sodium hydroxide) at a temperature between 150 to 200 °C. At this temperatures, the aluminium is dissolved in the solution as sodium aluminate in the extraction process. After separation of the residue by filtering, when the liquid is cooled gibbsite is precipitated and then it is seeded with fine-grained aluminum hydroxide crystals from previous extractions. The precipitation take 7-19 days without the addition of seed crystals.

This extraction process converts the aluminium oxide to soluble sodium aluminate, NaAlO2, which afterward converted into aluminum hydroxide and then into aluminum oxide.

Thus, we concluded that the material which is used as source for commercial production aluminum is bauxite ore.

learn more about ore:

brainly.com/question/10306443

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3 0
1 year ago
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