Representations of a mole (RAM 1 d.p.) | Exit Quiz | Oak National Academy

What does one mole of any substance contain?

• 6.02 × 10²³ particles

• 6.02 × 10²⁰ things

• 1,000 particles

• The mass of the substance in grams

Answer explanation

A mole of any substance contains 6.02 × 10²³ particles, according to Avogadro's number.

Order the following steps in the process of converting grams to moles.

• Divide the mass of the substance by its relative formula mass.

• Measure the mass of the substance.

• Calculate the substance's relative formula mass.

Answer explanation

First, you measure the substance's mass, then use its relative formula mass, and finally divide the mass by this value to find the moles.

Why is it important to choose the appropriate apparatus for measurements in chemistry?

• To complete experiments faster.

• To reduce measurement uncertainty.

• To use fewer chemicals.

• To make cleaning up easier.

Answer explanation

The right apparatus can significantly decrease the range within which the true value is expected to be found, enhancing accuracy.

Which of the following best describes the term "accuracy"?

• The precision of the measurement tools.

• The repeatability of measurements.

• How close a measured value is to the true value.

• The number of significant figures in a measurement.

Answer explanation

It's about the closeness of measurements to the standard or known value.

If the relative formula mass of sodium chloride (NaCl) is 58.5, what is the mass of 2 moles of NaCl? Give the answer to 3 significant figures.

Answer explanation

The mass of 2 moles of NaCl is 117 grams. This is calculated by multiplying the number of moles (2) by the relative formula mass (58.5).

Calculate the number of SO₄²⁻ ions in 34 g of Al₂(SO₄)₃. The answer is ___ × 10²³. Give your answer to 3 significant figures.

Answer explanation

The RFM of Al₂(SO₄)₃ is 342.3 In a 34 g sample, there are 0.0993 moles of Al₂(SO₄)₃ There are 0.298 moles of SO₄²⁻ ions since Al₂(SO₄)₃ contains 3 SO₄²⁻ ions 0.298 × 6.02 × 10²³ = 1.79 × 10²³