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3 years ago

What is the [OH^+] ina solution that has a pH=4.02

1 answer:

4 0

Answer is: concentration of hydroxide ions [OH⁻] is 1.047·10⁻¹⁰ M.
pH = 4.02.
pH = -log[H⁺].
[H⁺] = 10∧(-pH).
[H⁺] = 10∧(-4.02).
[H⁺] = 9.54·10⁻⁵ M; equilibrium concentration of hydrogen cations.
[H⁺] · [OH⁻] = 1·10⁻¹⁴ M².
[OH⁻] = 1·10⁻¹⁴ M² ÷ 9.54·10⁻⁵ M.
[OH⁻] = 1.047·10⁻¹⁰ M; equilibriom concentration of hydroxide anions.

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3 years ago

A mixture consists of sand and an aqueous salt

Alenkinab [10]

Answer is (4).

Explanation:

The given mixture contains an insoluble solid and an aqueous solution of salt. The insoluble solid is sand. 

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After filtering the mixture, we should collect the filtrate. Filtrate is the salt solution. By doing evaporation we can get the solid salt. 

First and second choices are wrong because after evaporating water filtration cannot be done and salt and sand will be mixed together.

Salt cannot be filtered out because the salt is soluble and it is in aqueous medium. Hence, third choice is wrong

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3 years ago

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Explanation:

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If aluminum is diffused into a thick slice of silicon with no previous aluminum in it at a temperature of 1100˚C for 8 hours, wh

RideAnS [48]

Answer:

8.354 nanometers

Explanation:

To treat a diffusive process in function of time and distance we need to solve 2nd Ficks Law. This a partial differential equation, with certain condition the solution looks like this:

$\frac{C_{s}-C{x}}{C_{s}-C_{o}}=erf(x/2\sqrt{D*t})$

Where Cs is the concentration in the surface of the solid

Cx is the concentration at certain deep X

Co is the initial concentration of solute in the solid

and erf is the error function

Then we solve right side,

$\frac{C_{s}-C{x}}{C_{s}-C_{o}}=\frac{1018atoms/cm3-1016atoms/cm3}{1018atoms/cm3}=0.001964$

And we need to look up the inverse error function of 0.001964 resulting in: 0.00174055

Then we solve for x:

$x=0.00174055*2*\sqrt{D*t} =0.00174055*2*\sqrt{2*10^{-12}cm^{2}/s*8h*3600s/h}=8.35464*10^{-7}cm$

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3 years ago

Each student in a class placed a 2.00 g sample of a mixture of Cu and Al in a beaker and placed the beaker in a fume hood. The s

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Answer:

Percentage mass of copper in the sample = 32%

Explanation:

Equation of the reaction producing Cu(NO₃) is given below:

Cu(s)+ 4HNO₃(aq) ---> Cu(NO₃)(aq) + 2NO₂(g) + 2H₂O(l)

From the equation of reaction, 1 mole of Cu(NO₃) is produced from 1 mole of copper. Therefore, 0.010 moles of Cu(NO₃) will be produced from 0.010 mole of copper.

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3 years ago