Percentage and Science Worksheet
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Percentage and Science Worksheet
Key formulas
Percentage error = (|approximate value − exact value| ÷ exact value) × 100
Percentage yield = (actual yield ÷ theoretical yield) × 100
Percentage composition = (mass of component ÷ total mass) × 100
Answer each question using the correct formula. Show your working clearly. Give answers to 1 decimal place where required.
1. A mixture contains 18 g of salt dissolved in 150 g of solution. What is the percentage concentration of salt in the solution?
2. A sample of rock contains 36 g of iron ore in a 240 g sample. What percentage of the rock is iron ore?
3. A chemistry student predicted they would produce 8.0 g of copper sulfate in a reaction but only obtained 6.4 g. Calculate the percentage yield.
4. A student measured the boiling point of water as 98.5 °C. The accepted value is 100.0 °C. Calculate the percentage error.
5. A student measured the density of aluminium as 2.85 g/cm³. The accepted value is 2.70 g/cm³. Calculate the percentage error to 1 decimal place.
6. A fertiliser contains 24 g of nitrogen in a 80 g bag. What percentage of the fertiliser is nitrogen?
7. In a biology survey, 340 out of 500 plants in a field were of species A. What percentage of the plants were species A?
8. A reaction was expected to produce 12.5 g of precipitate. The actual yield was 9.75 g. Calculate the percentage yield.
9. Air is approximately 78% nitrogen, 21% oxygen, and 1% other gases. In a 500 cm³ sample of air, what volume is nitrogen?
10. A student recorded the speed of sound as 355 m/s. The accepted value is 343 m/s. Calculate the percentage error to 1 decimal place.
11. A woodland habitat contained 120 oak trees and 80 birch trees. What percentage of the trees were oak?
12. A chemistry experiment produced 14.4 g of magnesium oxide. The theoretical yield was 16.0 g. Calculate the percentage yield.
13. A 250 g alloy contains 175 g of iron and 75 g of carbon. What percentage of the alloy is carbon?
14. A student estimated the acceleration due to gravity as 9.4 m/s². The accepted value is 9.8 m/s². Calculate the percentage error to 1 decimal place.
15. In a population study, 1,350 out of 1,800 individuals in a sample carried a particular gene. What percentage carried the gene?
16. A solar panel converts 18% of light energy into electrical energy. If it receives 2,500 J of light energy, how many joules of electrical energy does it produce?
17. A chemical reaction was 85% efficient. If the theoretical yield was 40 g, what mass of product was actually obtained?
18. A student measured the melting point of a substance as 52.8 °C. The true value is 55.0 °C. Calculate the percentage error to 1 decimal place.
19. A 200 cm³ seawater sample contains 7 cm³ of dissolved salt (by volume). What is the percentage concentration of salt?
20. In a genetics experiment, out of 480 offspring, 360 showed the dominant trait. What percentage showed the dominant trait? How does this compare to the expected 75%?
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