Aprotein was previously determined to contain 15.7 wt% nitrogen. a 647 m aliquot of a solution containing the protein was digested in boiling sulfuric acid. the solution was made basic and the liberated nh3 was collected in 10.00 ml of 0.0388 m hci. 3.83 ml of 0.0196 m naoh was required to react with the excess, unreacted hcl. calculate the protein concentration of the solution in units of milligrams per milliliter. number 0 mg protein ml solution

431.38 mg protein / mL

Explanation:

This is an example of the Kjeldahl method, for nitrogen determination. All nitrogen atoms in the protein were converted to NH₃ which then reacted with a known excess of HCl. This excess was later quantified via titration with NaOH.

First we calculate the total amount of H⁺ moles from HCl:

Now we calculate the excess moles of H⁺ (the moles that didn't react with NH₃ from the protein), from the titration with NaOH:

Now we substract the moles of H⁺ that reacted with NaOH, from the total number of moles, and the result is the moles of H⁺ that reacted with NH₃ from the protein:

With the moles of NH₃ we know the moles of N, then we can calculate the mass of N present in the aliquot:

From the exercise we're given the concentration of N in the protein, so now we calculate the mass of protein:

Finally we calculate the protein concentration in mg/mL, assuming your question is in 647 μL, we first convert that value into mL:

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.