The density of a substance that has a mass of 7.0 g and a volume of 3.4 cm3 is

2.05882 g/cm3

Explanation:

the formula p=m/V, or density (p) is equal to mass (m) divided by volume (V)

Answer is: c. 1.204 × 10²⁴ atoms of carbon.

n(C) = 2 mol; amount of substance of carbon.

Na = 6.02·10²³ 1/mol; Avogadro constant (the number of constituent particles, in this example atoms, that are contained in the amount of substance given by one mole).

N(C) = n(C) · Na.

N(C) = 2 mol · 6.02·10²³ 1/mol.

N(C) = 12.04·10²³ = 1.204·10²⁴; number of carbon atoms in a sample.