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Olegator [25]
2 years ago
15

What mass of ni2+ is produced in solution by passing a current of 67.0 a for a period of 14.0 h , assuming the cell is 90.0 % ef

ficient?
Chemistry
1 answer:
Ira Lisetskai [31]2 years ago
6 0
When we have the current = 67 coulombs/second

and mol of electrons of Ni2+= 2 

faraday's constant = 96500 

molar mass of Ni = 58.69 g/mol 

time (sec) = 14 h * 3600

∴ the mass of Ni2+ = 50400 sec * 67 coulombs/second * 1 mol of electrons / 96500 coulombs * 1 mol of Ni / 2 mol of electrons * 58.69 g/mol / mol of Ni

                               = 1027 g Ni
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A 0.1153-gram sample of a pure hydrocarbon was burned in a C-H combustion train to produce 0.3986 gram of CO2and 0.0578 gram of
Mars2501 [29]

<u>Answer:</u> The mass of carbon and hydrogen in the sample is 0.1087 g and 0.0066 g respectively and the percentage composition of carbon and hydrogen in the sample is 94.27 % and 5.72 % respectively.

<u>Explanation:</u>

The chemical equation for the combustion of hydrocarbon having carbon and hydrogen follows:

C_xH_y+O_2\rightarrow CO_2+H_2O

where, 'x' and 'y' are the subscripts of carbon and hydrogen respectively.

We are given:

Mass of CO_2=0.3986g

Mass of H_2O=0.0578g

Mass of sample = 0.1153 g

We know that:

Molar mass of carbon dioxide = 44 g/mol

Molar mass of water = 18 g/mol

  • <u>For calculating the mass of carbon:</u>

In 44g of carbon dioxide, 12 g of carbon is contained.

So, in 0.3986 g of carbon dioxide, \frac{12}{44}\times 0.3986=0.1087g of carbon will be contained.

  • <u>For calculating the mass of hydrogen:</u>

In 18g of water, 2 g of hydrogen is contained.

So, in 0.0578 g of water, \frac{2}{18}\times 0.0578=0.0066g of hydrogen will be contained.

To calculate the percentage composition of a substance in sample, we use the equation:

\%\text{ composition of substance}=\frac{\text{Mass of substance}}{\text{Mass of sample}}\times 100      ......(1)

  • <u>For Carbon:</u>

Mass of sample = 0.1153 g

Mass of carbon = 0.1087 g

Putting values in equation 1, we get:

\%\text{ composition of carbon}=\frac{0.1087g}{0.1153g}\times 100=94.27\%

  • <u>For Hydrogen:</u>

Mass of sample = 0.1153 g

Mass of hydrogen = 0.0066 g

Putting values in equation 1, we get:

\%\text{ composition of hydrogen}=\frac{0.0066g}{0.1153g}\times 100=5.72\%

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8 0
2 years ago
A student dissolved a sample in hexane, spotted it on to a TLC plate and eluted using ethyl acetate. After visualizing the TLC p
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1) Consider the following silica gel TLC plate of compounds A, B, and C developed in hexanes:

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2) You are trying to determine a TLC solvent system which will separate the compounds X, Y, and Z. You ran the compounds on a TLC plate using hexanes/ethyl acetate 95:5 as the eluting solvent and obtained the chromatogram below. How could you change the solvent system to give better separation of these three compounds?

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4) A student spots an unknown sample on a TLC plate. After developing in hexanes/ethyl acetate 50:50, he/she saw a single spot with an Rf of 0.55. Does this indicate that the unknown material is a pure compound? What can be done to verify the purity of the sample?

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5) Consider a sample that is a mixture composed of biphenyl, benzoic acid, and benzyl alcohol. The sample is spotted on a TLC plate and developed in a hexanes/ethyl acetate solvent mixture. Predict the relative Rf values for the three compounds in the sample.

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6) Plate A, below, represents the TLC chromatogram of a compound run in hexanes. The same compound was then spotted on a large TLC plate and again run in hexanes. Which TLC plate, B, C, or D, correctly represents how far the compound would run on the longer plate?

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Back to TLC

Original content © University of Colorado at Boulder, Department of Chemistry and Biochemistry.
The information on these pages is available for academic use without restriction.
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A scientist is wondering why a certain region in the ocean doesn't have maximum phytoplankton growth, despite having plenty of n
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Answer:

C The water had adequate nitrogen and phosphorus, so it is likely iron limited.

Explanation:

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They require nitrogen, phosphorus and trace amount of iron to survive.

From the scientist's results after testing the water for nitrogen and phosphorus,there are reasonable amount of these elements.

Therefore insufficient iron in the water is the reason why he could find plenty phytoplankton in the ocean.

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Cr{3+} + 3 NaF → CrF3 + 3 Na{+} <span>

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