Expert Chemistry Tutoring

Q1 (1 mark)

Define relative atomic mass.

Q2 (2 marks)

Explain why the relative atomic mass of neon is a whole number.

Q3 (3 marks)

Calculate the relative atomic mass of magnesium from the following data:

- 78.99% of Mg-24 (relative atomic mass 24)

- 10.00% of Mg-25 (relative atomic mass 25)

- 11.01% of Mg-26 (relative atomic mass 26)

Q4 (2 marks)

What is the mass (in grams) of 2.00 mol of hydrogen atoms? (Relative atomic mass of hydrogen: 1.0)

Q5 (3 marks)

The empirical formula of an oxide of magnesium is MgO. Calculate its molar mass.

Q6 (1 mark)

Which of the following statements is true about the relative atomic mass of a mixture of isotopes?

(a) It is always a whole number.

(b) It is the average mass of the isotopes.

(c) It is the mass of the most abundant isotope.

(d) It changes depending on the temperature of the sample.

Q7 (2 marks)

Why is it important to use relative atomic masses rather than atomic masses in calculations?

Q8 (3 marks)

A sample of an element contains three isotopes:

- 60% of an isotope with a mass of 35 atomic mass units

- 15% of an isotope with a mass of 37 atomic mass units

- 25% of an isotope with a mass of 39 atomic mass units

Calculate the relative atomic mass of the element.

Q9 (1 mark)

What is the relative atomic mass of an element if one of its isotopes has a mass of 120 atomic mass units and a relative abundance of 57%?

Q10 (4 marks)

A compound has the following percentage composition by mass:

- 40.0% Carbon (C)

- 6.7% Hydrogen (H)

- 53.3% Oxygen (O)

Calculate the empirical formula of the compound. (Relative atomic masses: C: 12.01, H: 1.01, O: 16.00)