Expert Chemistry Tutoring

Q1. Knowledge Recall (1 mark)

Define the term 'mole'.

Q2. Application of knowledge (2 marks)

Explain how the mass of a sample can be determined using the mole concept.

Q3. Data Analysis/Calculations (3 marks)

A sample of sodium chloride has a mass of 2.5 g. Calculate the number of moles of sodium chloride present. (Relative atomic mass: Na = 23, Cl = 35.5)

Q4. Knowledge Recall (2 marks)

State the formula for calculating the molar mass of a substance.

Q5. Application of knowledge (3 marks)

A solution containing 1.5 mol of NaCl is diluted to a volume of 500 mL. Calculate the molarity of the new solution.

Q6. Data Analysis/Calculations (4 marks)

A student needs to prepare 250 mL of a 0.2 M solution of sodium hydroxide. Calculate the mass of sodium hydroxide that is required. (Relative molecular mass: NaOH = 40)

Q7. Knowledge Recall (1 mark)

Define the empirical formula of a compound.

Q8. Application of knowledge (3 marks)

Explain how to determine the empirical formula of a compound from its percentage composition.

Q9. Data Analysis/Calculations (3 marks)

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. Calculate its empirical formula.

Q10. Application of knowledge (3 marks)

Discuss the limitations of using the mole concept in the determination of atomic masses.