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Ira Lisetskai [31]
2 years ago
15

If atoms are so tiny how do we know they exist

Chemistry
1 answer:
Aleksandr [31]2 years ago
5 0

There are three ways that scientists have proved that these sub-atomic particles exist. They are direct observation, indirect observation or inferred presence and predictions from theory or conjecture. Scientists in the 1800's were able to infer a lot about the sub-atomic world from chemistry.

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which of the following amino acids are used to measure the protein concentration by UV? A. His B. Pro C. Trp D. Phe E. Tyr
Goryan [66]

Answer:

C. Trp D. Phe E. Tyr

Explanation:

The concentration of a protein has a direct relation with absorbance of the protein in a UV spectrophotometer. The formula which relates concentration with absorbance is described as under:

                A = ∈ x c x l

where, A = Absorbance

            ∈ = Molar extinction co-efficient

            c  = Concentration of absorbing species i.e. protein

             l  = Path length of light

       

Tryptophan (Trp), phenylalanine (Phe ) and tyrosine (Tyr) are three aromatic amino acids which are used to measure protein concentration by UV. It is mainly because of tryptophan (Trp), protein absorbs at 280 nm which gives us an idea of protein concentration during UV spectroscopy.

The table depicting the wavelength at which these amino acids absorb and their respective molar extinction coefficient is as under:

Amino acid                Wavelength            Molar extinction co-efficient (∈)

Tryptophan                     282 nm                        5690

Tyrosine                          274 nm                        1280

Phenylalanine                 257 nm                        570

In view of table above, we can easily see that Molar extinction co-efficient (∈) of Tryptophan is highest amongst all these 3 amino acids that is why it dominates while measuring concentration.

7 0
3 years ago
Common units of electrical force are: A coulombs B Newtons C meters
dybincka [34]

b is the correct answer

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The stock solution contains 10.5 moles of HCl per litre. A 5.5 litre solution of 2.5M HCl contains 5.5x2.5 = 13.75moles of HCl. Since every litre of stock solution provides 10.5M HCl, the amount of stock solution needed is 13.75/10.5 = 1.309L. Therefore you would dilute 1.309L of stock solution to 5.5L
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3 years ago
What information does the first quantum number of an electron give?
bazaltina [42]

Answer:

с

Explanation:

the first quantum number of an electron gives the information about the energy level the electron is in

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