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3 years ago

Why must the line of origin be drawn in pencil instead of pen on the chromatography strip?

Chemistry

1 answer:

Kruka [31]3 years ago

5 0

Answer:

Because if you use pen, your chromatography will separate also the colors of the pen and not just your sample.

Explanation:

The pencil since is carbon as simple element, is solid and is not dissolved in solvents like commonly are used in paper chromatography, it will not interrupt the separation of the compounds in your mixture, otherwise, your results will be confuse because you are not sure if the spots that you observe is due to the ink pen or due to the mixture that you want to separate.

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A 3.96x10^-24 M solution of compound A exhibited an absorbance of 0.624 at 238 nm in a 1.000-cm cuvet; a blank solution containi

viktelen [127]

Actual question from source:-

A 3.96x10-4 M solution of compound A exhibited an absorbance of 0.624 at 238 nm in a 1.000 cm cuvette. A blank had an absorbance of 0.029. The absorbance of an unknown solution of compound A was 0.375. Find the concentration of A in the unknown.

Answer:

Molar absorptivity of compound A = $1502.53\ {Ms}^{-1}$

Explanation:

According to the Lambert's Beer law:-

$A=\epsilon l c$

Where, A is the absorbance

l is the path length

$\epsilon$ is the molar absorptivity

c is the concentration.

Given that:-

c = $3.96\times 10^{-4}\ M$

Path length = 1.000 cm

Absorbance observed = 0.624

Absorbance blank = 0.029

A = 0.624 - 0.029 = 0.595

So, applying the values in the Lambert Beer's law as shown below:-

$0.595=\epsilon\times 1.000\ cm\times 3.96\times 10^{-4}\ M$

$\epsilon=\frac{0.595}{3.96\times 10^{-4}}\ {Ms}^{-1}=1502.53\ {Ms}^{-1}$

Molar absorptivity of compound A = $1502.53\ {Ms}^{-1}$

4 0

3 years ago

A weight of 0.27 kilogram is 1. 0.00027 mg 2. 270 mg 3. 27 mg 4. 2.7 × 105 mg

julia-pushkina [17]

The answer is: 4) " 2.7 * 10⁵ mg " .
________________________________________________________
Explanation:
________________________________________________________
Since all answer choices given are in "mg" ("milligrams"); we need to convert our given value, "0.27 kg" ("kilograms") to "mg" ("milligrams").
________________________________________________________
Note the following "exact value" conversions:
________________________________________________________
1000 mg = 1 g ;
1000 g = 1 kg.

(0.27 kg) (1000 g / 1 kg) (1000 mg/1 g) = __?__ mg ;
_____________________________________________________
The units of "kg", and "g" cancel to "1" and we are left with:
________________________________________________
0.27 * 1000 * 1000 mg = 270,000 mg = 2.7 * 10⁵ mg ; which is:
_______________________________________________________
→ Answer choice: # 4 .
_______________________________________________________

8 0

3 years ago

What is restriction enzymes and what is it’s purpose?

Eddi Din [679]

Answer: Endonuclease enzymes used in molecular biology that cut DNA at specified points.

Explanation:

Enzymes are specific protein types which bind to a substrate within a reaction, to increase the rate of reaction within the solution- they speed up the rate of reaction.

Restriction enzymes are bacteria-derived enzymes; these make cuts on deoxyribonucleic acid molecules or DNA. These are also called restriction endonucleases. They are utilized in molecular biology for DNA cloning and sequencing and cut DNA into smaller pieces called fragments.

Restriction enzymes make directed cuts on DNA molecules. They precisely target sites on DNA to produce mostly identical or homogenous, discrete fragments of equal sizes, producing blunt or sticky ends. In order to do this, they recognize sequences of nucleotides that correspond with a complementary sequence on the endonuclease called restriction sites.

There are several kinds that may require cofactors (chemical or metallic compounds that aid in enzyme activity) :

Type I: cleave far away from the recognition site; require ATP and SAMe S-Adenosyl-L-Methionine

Type II: cleave near to the site; require Magnesium

Type III: cleave near to the site; require ATP which is not hydrolysed but SAMe S-Adenosyl-L-Methionine is optional

Type IV: cleavage targeted to DNA that have undergone post transcriptional modification through certain types of methylation (addition of a methyl group)

7 0

2 years ago

100POINTS!!!! Label each reaction to either homogeneous OR heterogeneous

liraira [26]

First is homogeneous and so is the third. second is heterogeneous

8 0

2 years ago

What is the main reason that attitudes are more often revealed in spoken rather than written language?

musickatia [10]

I believe the answer is D.

6 0

3 years ago