You are instructed to create 900. mL of a 0.29 M phosphate buffer with a pH of 7.8. You have phosphoric acid and the sodium salts NaH2PO4, Na2HPO4, and Na3PO4 available. (Enter all numerical answers to three significant figures.)

H3PO4(s) + H2O(l) <> H3O+(aq) + H2PO4−(aq) Ka1 = 6.9 ✕ 10−3
H2PO4−(aq) + H2O(l) <> H3O+(aq) + HPO42−(aq) Ka2 = 6.2 ✕ 10−8
HPO42−(aq) + H2O(l) <> H3O+(aq) + PO43−(aq) Ka3 = 4.8 ✕ 10−13

Which of the available chemicals will you use for the acid component of your buffer?

A. H3PO4
B. NaH2PO4
C. Na2HPO4
D. Na3PO4

Which of the available chemicals will you use for the base component of your buffer?

A. H3PO4B. NaH2PO4C. Na2HPO4D. Na3PO4

B and C

Explanation:

When we have to do a buffer solution we always have to choose the reaction that has the pKa closer to the desired pH value. When we find the pKa values we will obtain:

The closer value is pKa2 with a value of 7.2. Therefore we have to use the second reaction. In which   is the acid and is the base. Therefore the answer for the first question is B and the answer for the second question is C.

the law of conservation of mass states that in a chemical reaction, the total mass of reactants is equal to the total mass of products. because atoms are only rearranged in a chemical reaction, there must be the same number of sodium atoms and chlorine atoms in both the reactants and products

c. 75.7

i think that is the right