Question

What is the mass of a magnesium block that measures 2.5cm x 3.5cm x 1.5cm?

Answer 1

Answer: 22.8 g

Explanation:

1) density = mass / volume ⇒ mass = density × volume

2) density of magnesium = 1.74 g/cm³ (from internet)

3) volume of a block = length × width × depth

  volume of the magnesium block = 2.5cm × 3.5 cm × 1.5 cm = 13.125 cm³

4) mass of the magnesium block = 1.74 g/cm³ × 13.125 cm³ = 22.8375 g.

Rounding to 3 significant figures, mass = 22.8 g ← answer

Answer 2

The mass of the magnesium block is found to be 22.8 g.

Density of a substance is defined as mass per unit volume.

Calculate the volume V of the magnesium block using the dimensions given in the problem.

$V=(2.5cm)(3.5cm)(1.5cm)\\ =13.125cm^3$

Magnesium has a density ρ of 1.74g/cm³. This can be taken from the standard tables.

Since density is mass per unit volume,

$\rho=\frac{m}{V}$

The mass of the block is therefore given by,

$m=\rho V$

Substitute  1.74g/cm³for  ρ and 13.125 cm³for V.

$m=\rho V=(1.74g/cm^3)(13.125cm^3)=22.8375g$

The mass of the magnesium block is found to be 22.8 g.