Calculate the mass percent of phosphorus in a strand of DNA that consists of equal amounts of each of the four N-bases.

8.62%

Explanation:

The DNA is composed of the grouping of the nucleotides, which are composed of one phosphate group (PO₄⁻²), one molecule of sugar (deoxyribose), and one N-base, which can be adenine, guanine, cytosine, and thymine.

Let's assume as a calculus basis, 1 mol of the compound, and, because it has the same amount of each N-base, 1 molecule of each N-base nucleotide.

The molar mass of phosphate is 95 g/mol, the molar of the deoxyribose is 134 g/mol, the molar mass of adenine is 135 g/mol, of guanine, is 151 g/mol, of cytosine is 111 g/mol, and of thymine is 126 g/mol.

So, the molar masses of the nucleotide of each N-base are:

Adenine: 95 + 134 + 135 = 364 g/mol

Guanine: 95 + 134 + 151 = 380 g/mol

Cytosine: 95 + 134 + 111 = 340 g/mol

Thymine: 95 + 134 + 126 = 355 g/mol

Thus, the mol with one of each of these N-bases has mass 1439 g (364 + 380 + 340 + 355). The molar mass of phosphorus is 31 g/mol, so 1 mol has 31 g. Each nucleotide has one phosphorus, so the total mass of phosphorus is 124 g (4*31).

The percent of phosphorus is then:

(124/1439) * 100% = 8.62%