Consider the substances below.

• 1 mol of beryllium

• 1 mol of salt

• 1 mol of water

• 1 mol of hydrogen

Which statement is true about these substances?

1) They have exactly the same mass.

2) They have different numbers of particles.

3) They have the same number of atoms.

4) They have different masses.

1) is not true as we know that 1 mol of a substance is equal to its RFM in grams

2) is true as we know that the number of particles in one mole of any substance is avagadros constant (6.02*10^23)

3) is not true, from the previous statement we can tell that as water is comprised of 3 different atoms it will have 3 times the number of atoms

4) is true as berylium will have a mass of 4g, water of 10g and hydrogen 2g or 1g depending on whether it is the gas or the element. The salt will vary as it could be comprised of lots of different combinations.

Therefore 2 and 4 are correct