Chemical Formulae, Equations, Calculations Quiz
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5 questions, one answer each
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1. What is the unit for amount of substance?
- A. Gram
- B. Mole
- C. Litre
- D. Newton
2. Which formula correctly relates moles, mass and relative formula mass?
- A. Moles = mass × Mr
- B. Moles = mass ÷ Mr
- C. Moles = Mr ÷ mass
- D. Mass = moles ÷ Mr
3. A reaction has a theoretical yield of 20 g but only 15 g of product is actually obtained. What is the percentage yield?
- A. 25%
- B. 65%
- C. 75%
- D. 133%
4. A compound is found to contain 0.2 mol of element X for every 0.6 mol of element Y. What is the empirical formula ratio of X:Y?
- A. 1:1
- B. 1:3
- C. 3:1
- D. 2:6
5. A student wants to determine the empirical formula of a metal oxide by combustion, but their metal sample was not fully oxidised before the final mass was recorded. What effect would this most likely have on the calculated formula?
- A. No effect, since mass of metal is unchanged
- B. The oxygen content would appear lower than it actually is, giving an inaccurate ratio
- C. The formula would show more oxygen atoms than the metal actually has
- D. It would only affect the melting point, not the formula