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3 years ago

Which four of the following statements about amino acids are true?

Chemistry

1 answer:

k0ka [10]3 years ago

6 0

Answer: • Phe can undergo oxidation to form Tyr.

• The Ala side chain does not form hydrogen bonds with other amino acids.

• Thr and Ser are polar amino acids.

• Lysine has one stereocenter (chiral center).

Explanation:

Amino acids are simply organic compounds which are known to contain carboxyl and amine functional groups and the main elements that are found in an amino acid are oxygen, carbon, hydrogen, and nitrogen.

The true statements about amino acids are:

• Phe can undergo oxidation to form Tyr.

• The Ala side chain does not form hydrogen bonds with other amino acids.

• Thr and Ser are polar amino acids.

• Lysine has one stereocenter (chiral center).

It should be noted that Methionine is not a thiol but rather a thio ether. Also, proline is simply a neutral amino acid and the statement that proline has an overall charge at physiological

pH(7.4) is false.

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When 69.9 g heptane is burned it releases __ mol water.

professor190 [17]

Answer:

1) When 69.9 g heptane is burned it releases 5.6 mol water.

2) C₇H₁₆ + 11O₂ → 7CO₂ + 8H₂O.

Explanation:

Firstly, we should balance the equation of heptane combustion.

The balanced equation is: C₇H₁₆ + 11O₂ → 7CO₂ + 8H₂O.

This means that every 1.0 mole of complete combustion of heptane will release 8 moles of H₂O.

We need to calculate the no. of moles in 69.9 g of heptane that is burned using the relation: n = mass/molar mass.

n of 69.9 g of heptane = mass/molar mass = (69.9 g)/(100.21 g/mol) = 0.697 mol ≅ 0.7 mol.

Using cross multiplication:

1.0 mol of heptane releases → 8 moles of water.

0.7 mol of heptane releases → ??? moles of water.

∴ The no. of moles of water that will be released from burning (69.9 g) of water = (0.7 mol)(8.0 mol)/(1.0 mol) = 5.6 mol.

∴ When 69.9 g heptane is burned it releases 5.6 mol water.

5 0

3 years ago

Using the following thermochemical data, what is the change in enthalpy for the following reaction: 3H2(g) + 2C(s) + ½O2(g) → C2

sweet [91]

It would be -277.6 KJ/mol

7 0

3 years ago

Read 2 more answers

Consider the following intermediate chemical equations.

olga nikolaevna [1]

I think that would be the third one

5 0

3 years ago

Read 2 more answers

October 15, 2018 at 1:49 PM Dioxybenzone is a compound found in sunscreen, and only contains carbon, oxygen, and hydrogen. Analy

-Dominant- [34]

Answer:

Molecular formula for Dioxybenzone is C₁₄H₁₂O₄

Explanation:

Percent composition:

In 100 g of compound → 4.92 g are H

In 100 g of compound → 26.8 g are O

In 100 g of compound → 68.28 g are C

Let's convert the mass to moles by molar mass:

4.92 g / 1 g/mol = 4.92 moles H

26.8 g / 16 g/mol = 1.67 moles O

68.28 g / 12 g/mol = 5.69 moles C

Now we can apply a rule of three:

100 g of compound have 4.92 moles H, 1.67 moles O, 5.69 moles C

244.25 g of compound must have:

(244.25 g . 4.92 m) / 100 g = 12 moles H

(244.25 g . 1.67 m) / 100 g = 4 moles O

(244.25 g . 5.69 m) / 100 g = 14 moles of C

4 0

3 years ago

Sometimes, based on the electron configurations of the elements involved, a possible chemical formula for a compound can be pred

Nadusha1986 [10]

Answer:

D)the first ionization energy (IE1) of B is most probably lower than the first ionization energy (IE1) of A

Explanation:

As mentioned the possible chemical formula for a compound can be predicted from electron configurations of the elements.

The first element 'A' has electronic configuration as "[core]ns²

It means it has two valence electrons and it can give those valence electrons to attain noble gas or full filled stability.

So the element is most likely to form a dipositive ion.

Now for element B the configuration is :[Core]ns²np⁵

thus it has seven valence electrons and it will most likely to accept an electron to gain full filled stability. So B will form a mono negative ion.

The possible formula will be AB₂ [Like MgCl₂]

So the false statements are:

D)the first ionization energy (IE1) of B is most probably lower than the first ionization energy (IE1) of A : the first ionization energy of A will be lower than B as B cannot give an electron easily.

The other statements are correct:

A) element A serves as the reducing agent in the reaction to form AxBy : As A will lose electrons so it will acts as reducing agent and itself gets oxidized

B) yes it is whole number as calculated above.

C) x + y = 1+2 = 3

E) Already calculated that B has oxidation state of -1.

4 0

3 years ago