Questions and Answers
What is the percentage of salt (by mass) in a mixture made by combining 1.13 lb of salt and 5.15 lb of water?
18%
How many kilograms of ore are needed to obtain 45.0 g of nickel from an ore that is 34.4% nickel by mass?
0.131 kg
How many grams of salt are needed to make 471 g of salt water that is 36.5% salt by mass?
172 grams
What fraction of the mass of the human body is potassium if a 70.0 kg person has 0.25 kg of potassium?
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What percentage of the mass of the human body is potassium if it is 0.25 kg in a 70.0 kg person?
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What is the mass of phosphorus in a 49 kg person, given that there are 0.78 kg of phosphorus in a 70 kg person?
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What is the weighted average of the values given: 4.00 = 75.0%, 5.00 = 15.0%, 6.00 = 10.0%?
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What is the overall grade of a student who scored 82.7% on exams, 71.4% on quizzes, 90.0% on homework, and 100.0% on class participation, given their respective weights?
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Study Notes
Mixture Composition
- To calculate the percentage of salt in a mixture, use the formula: %composition = (mass of component / total mass) × 100%
- For a mixture of 1.13 lb of salt and 5.15 lb of water, the salt percentage is 18%.
- Calculation: % composition = (1.13 lb) / (1.13 lb + 5.15 lb) × 100% = 18.0%
Nickel Content in Ore
- An ore that is 34.4% nickel by mass requires specific mass calculation to obtain a desired quantity of nickel.
- To acquire 45.0g of nickel:
- Use the relationship 34.4g Ni per 100g ore.
- Calculation: 45.0g Ni × (100g ore / 34.4g Ni) = 131g ore.
- Convert to kilograms: 131g = 0.131 kg of ore needed.
Salt in Salt Water
- To determine the mass of salt in salt water, apply the percentage composition calculation.
- For 471g of salt water at 36.5% salt by mass:
- Mass of salt needed = 36.5% of 471g = 172g salt.
Elements in the Human Body
- The human body consists of multiple elements; primarily, it is comprised of oxygen and carbon.
- Specific masses of elements for a 70.0 kg person include:
- Potassium: 0.25 kg
- Phosphorus: 0.78 kg
- Questions regarding potassium:
- Fraction of the body mass: 0.25 kg out of 70 kg = 0.0036
- Percentage: (0.25 kg / 70 kg) × 100% = 0.36%
- For a 49 kg person, the phosphorus mass is calculated as:
- Mass = (0.78 kg / 70 kg) × 49 kg = 0.55 kg.
Weighted Average Calculation
- To find the weighted average of values:
- 4.00 has a weight of 75.0%
- 5.00 has a weight of 15.0%
- 6.00 has a weight of 10.0%
- Resulting weighted average: 4.35.
Overall Course Grade Calculation
- In a course, assignments contribute different percentages to the final grade:
- Exams: 50%
- Quizzes: 30%
- Homework: 15%
- Class Participation: 5%
- Example scores:
- Exams: 82.7%
- Quizzes: 71.4%
- Homework: 90.0%
- Participation: 100.0%
- Overall grade calculation results in: 81.3%.
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Description
This quiz covers the calculation of percent composition in mixtures, focusing on examples involving salt and water. You'll learn how to determine the percentage of a specific component by mass and apply this knowledge to real-world scenarios. Test your understanding of mass composition calculations.
