The density is 5.4 g/mL and the volume is 12.9 mL.

69.66 g

Explanation:

We have the following from the question;

Density of the substance = 5.4 g/ml

Volume of substance = 12.9 ml

Mass of substance= the unknown

Since we have both density and volume of the substance, the question must be for us to obtain the mass of the substance, hence;

Density= mass/volume

Mass= Density × volume

Mass = 5.4 g/ml × 12.9 ml

Mass= 69.66 g

they are both synthetic elements

explanation:

d