Question

The natural abundances of elements in the human body, expressed as percent by mass, are oxygen (o), 65 percent; carbon (c), 18 percent; hydrogen (h), 10. Percent; nitrogen (n), 3.0 percent; calcium (ca), 1.6 percent; phosphorus (p), 1.2 percent; all other elements, 1.2 percent. Enter your answers in scientific notation. Calculate the mass in grams of each element in the body of a 64−kg person.

Answer 1

Answer:

O: 4.2 × 10⁴ g

C: 1.2 × 10⁴ g

H: 6.4 × 10³ g

N: 1.9 × 10³ g

Ca: 1.0 × 10³ g

P: 7.7 × 10² g

Other elements: 7.7 × 10² g

Explanation:

Natural abundances of elements in the human body (in percent by mass)

• oxygen (O), 65%

• carbon (C), 18%

• hydrogen (H), 10%

• nitrogen (N), 3.0%

• calcium (Ca), 1.6%

• phosphorus (P), 1.2%

• all other elements, 1.2%

The mass of a body is 64 kg = 64 × 10³ g = 6.4 × 10⁴ g. We can calculate the mass of each element by multiplying the body weight by the mass percent of each element.

O: 6.4 × 10⁴ g × 65% = 4.2 × 10⁴ g

C: 6.4 × 10⁴ g × 18% = 1.2 × 10⁴ g

H: 6.4 × 10⁴ g × 10% = 6.4 × 10³ g

N: 6.4 × 10⁴ g × 3.0% = 1.9 × 10³ g

Ca: 6.4 × 10⁴ g × 1.6% = 1.0 × 10³ g

P: 6.4 × 10⁴ g × 1.2% = 7.7 × 10² g

Other elements: 6.4 × 10⁴ g × 1.2% = 7.7 × 10² g

Answer 2

It is given that the person weighs 62 kg = 62,000 g

Natural abundances in mass percent are:

O = 65%

C = 18%

H = 10%

N = 3.0%

Ca = 1.6%

P = 1.2%

Corresponding weights of the elements are:

O = 65/100 * 62000 g = 40.30 * 10^3 g

C = 18/100 * 62000 g = 11.16 * 10^3 g

H = 10/100 * 62000 g = 62.00 * 10^2 g

N = 3.0/100 * 62000 g = 18.60 * 10^2 g

Ca = 1.6/100 * 62000 g = 9.92 * 10^2 g

P = 1.2/100 * 62000 g = 7.44 * 10^2 g