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Gwar [14]
3 years ago
10

In the spectrophotometric analysis of benzene, the calibration curve has a slope of 195 AU/M and an intercept of 0.079 AU. If an

unknown has an absorbance of 0.517 AU, what is the concentration of benzene in the sample?
a. 2.09 x10^-4 M
b. 2.25 x 10^-3 M
c. 2.65 x 10^-3 M
d. 0.438 M
Chemistry
1 answer:
zloy xaker [14]3 years ago
5 0

Answer:

b. 2.25 x 10^-3 M

Explanation:

Please remember that according to Beer´s, law the absorbance is given by

A = Acl where A = absorbance, A is the molar absorptivity, c is concentration (M) and l is the path length of the cubette of used.

Now it follows from this equation that the absorbance is linearly related to concentration and what we are being told is that experimentally the linear equation obtained during calibration was:

A = 195 c + 0.079

We have all the information required to solve this question to solve for c:

0.517 = 195 c + 0.079 ⇒ c = (0.517 - 0.079) AU/ 195 AU/M = 2.25 x 10⁻³ M

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A reaction is second order respect to the reactant A. If the reaction is 85% complete in 12 minutes, how long would it take for
AnnZ [28]

Answer:

e. 22s

Explanation:

Initial Concentration = 100

Final concentration = 15 ( Since the reaction is 85% complete)

Time = 12 minutes = 720 seconds

The integrated rate law for second order reactions is given as;

1 / [A] = (1 / [A]o) + kt

Making k subject of interest, we have;

kt = (1 / [A] ) - (1 / [A]o )

k = (1 / [A] ) - (1 / [A]o ) / t

k = [(1/ 15) - (1 / 100) ] / 720

k = (0.0667 - 0.01 ) / 720

k = 0.0567 / 720

k = 7.875e^-5

How long would it take for the reaction to be 15% complete?

Final concentration = 85 (Since the reaction would be 15% complete)

The integrated rate law for second order reactions is given as;

1 / [A] = (1 / [A]o) + kt

Making t subject of interest, we have;

kt = (1 / [A] ) - (1 / [A]o )

t = (1 / [A] ) - (1 / [A]o ) / k

t = [(1 / 85 ) - (1 / 100) ] / 7.875e^-5

t = (0.0117 - 0.01 ) / 7.875e^-5

t = 0.001765 / 7.875e^-5

t = 22.41 seconds

Corect option = E.

3 0
3 years ago
The reduction of aldehydes, ketones, organic acids and their derivative of the process of alcohols is used for
ikadub [295]

Answer:

Widening of blood vessels.

Explanation:

The reduction of aldehydes, ketones, organic acids causes the formation of alcohols that is used for different process in the human body. This alcohol increase the width of the blood vessels as it enters the bloodstream causing greater flow of blood to the skin surface as well as temporary feeling of warmth. It also increased heat loss and rapid body temperature decrease that produces cooling effect in the body.

8 0
3 years ago
A sample of a compound contains ​0.300 mol​ ​of carbon​ and ​1.20 mol​ ​of hydrogen​. What is the ​empirical formula of the comp
Margarita [4]

Answer:

CH4

Explanation:

The number of moles of carbon and hydrogen has been given as follows:

C = ​0.300 mol​ ​

H = ​1.20 mol

Next, we divide each mole value by the smallest (0.300)

C = 0.300 ÷ 0.300 = 1

H = 1.20 ÷ 0.300 = 4

The empirical ratio of Carbon and Hydrogen is 1:4, hence, the empirical formula is CH4

3 0
3 years ago
Hydrogen 3 has a half life of 12.32 years a sample of h-3 weighing 3.02 grams is left for 15.0 years what will the final weight
yawa3891 [41]

Answer:

The final mass of sample is 1.3 g.

Explanation:

Given data:

Half life of H-3 = 12.32 years

Amount left for 15.0 years = 3.02 g

Final amount = ?

Solution:

First all we will calculate the decay constant.

t₁/₂ = ln² /k

t₁/₂ =12.32 years

12.32 y =  ln² /k

k = ln²/12.32 y

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ln (3.02 g/ A) = 0.8439

3.02 g/ A = e⁰°⁸⁴³⁹

3.02 g/ A = 2.33

A = 3.02 g/ 2.33

A = 1.3 g

The final mass of sample is 1.3 g.

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