Which substance has a mass is 13.5 grams, and its volume is 5 cm 3.

Substance is Aluminium

Explanation:

We are given;

Mass; m = 13.5 grams

Volume; V = 5 cm³

Formula for density is;

density = m/V

Density = 13.5/5

Density = 2.7 g/cm³

From the table attached, we can see that the element with a corresponding density of 2.7 is Aluminium

n+h→nh3

we must remember that nitrogen and hydrogen are both diatomic molecules in their standard gas form. this adjusts the equation to

n2+h2→nh3

now we need to adjust coefficients in order to balance the atoms on each side of the equation. currently we have 2 atoms of nitrogen and 2 atoms of hydrogen on the reactant side and 1 atom of nitrogen and 3 atoms of hydrogen on the product side.

we can balance the hydrogens by placing a coefficient of 2 in front of ammonia and a coefficient of 3 in front of the hydrogen.

n2+3h2→2nh3

this gives us 6 hydrogen on each side and coincidentally the nitrogens now equal 2 on each side.