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Lesson Worksheet: Determining Purity Chemistry
In this worksheet, we will practice determining the purity of a substance based on its proportion by mass and physical properties.
An impure sample of aluminum bromide contains contaminants by weight. What is the percentage purity of the sample?
Which of the following statements best describes what an impurity is?
- AAn unwanted substance mixed within a desired substance
- BA wanted substance mixed within a desired substance
- CA substance finely dispersed in another substance
- DA substance dissolved in another substance
- EA substance that can be separated from another substance
Which of the following is an effect that impurities do not typically have on the boiling or melting point of a substance?
- AMaking the melting point occur over a larger temperature range
- BDeviating from the reference value for the melting or boiling point
- CMaking the boiling point occur sharply at a definite temperature
- DIncreasing the boiling point
- EDecreasing the melting point
A student obtains a sample of water and wants to test its purity by determining its melting and boiling points.
What results should the student expect to find if the sample is pure?
- AThe sample boils at exactly and freezes at exactly .
- BThe sample boils between and and freezes between and .
- CThe sample boils and freezes over a large temperature range.
- DThe sample boils over a large temperature range but freezes at exactly .
How can the student obtain pure water if the sample is found to contain soluble impurities?
The image below shows a labeled bottle of orange juice.
Why might the company claim the orange juice is pure?
- AIt has a pH of 7, making it neutral.
- BIt contains no added or artificial products.
- CIt is made up of any one type of compound.
- DThe solution is completely orange in color.
- EThe oranges were organically grown.
Why might a chemist say the orange juice is not pure?
- AIt only contains an artificial substance.
- BThe particles are free to move around each other.
- CIt does not contain just one substance.
- DIt is slightly acidic.
- EThe solution is not colorless.
5 g of salt is mixed with 20 g of powdered sugar. Which of the following statements best describes this mixture?
- ASugar is considered an impurity, and its percentage is .
- BEither sugar or salt can be an impurity interchangeably.
- CSalt is considered an impurity, and its percentage is .
- DSugar is considered an impurity, and its percentage is .
- ESalt is considered an impurity, and its percentage is .