Question

Given the following densities at 25°C magnesium: 1.7 g/cm3 graphite: 1.8 g/cm3 iron: 7.9 g/cm3 A block of iron has a mass of 819 g. What is the mass of a block of magnesium that has the same volume as the block of iron?

Answer 1

Answer:

Mass of block of Magnesium = 180 g

Explanation:

The question gives the following data:

• Density of Magnesium = 1.7 g/cm³

• Density of Graphite = 1.8 g/cm³

• Density of Iron = 7.9 g/cm³
• Mass of block of Iron = 819 g

Density is defined as

density = mass / volume

The question asks for the mass of a block of magnesium with a volume equal to the volume of the block of iron, so lets calculate this volume:

From the density formula:

volume = mass / density

Volume of Magnesium = Volume of Iron = mass of Iron / density of Iron

Volume of Magnesium = 819 g / 7.9 g/cm³

Now lets calculate Mass of Magnesium, we get from the formula:

mass = density x volume

Mass of Magnesium = density of Magnesium x volume of Magnesium

Mass of Magnesium = 1.7 g/cm³  x (819 g / 7.9 g/cm³) = 176.24 g

With correct number of significant figures it would be 180 g