Admin Table of Contents
- 1 How can we check whether the given solid substance is pure or not?
- 2 How can you separate a pure substance?
- 3 What are two ways of testing purity of a substance?
- 4 How can you predict the state of a substance?
- 5 How can melting and boiling points determine the identity of a substance?
- 6 How do you determine the purity of a sample?
How can we check whether the given solid substance is pure or not?
To determine if a substance is pure in school laboratories, we can check the substance’s melting or boiling points or use chromatography (see Separation Techniques). A pure solid has a constant/fixed melting point. ie. it will melt completely at one temperature only.
How can you separate a pure substance?
A pure substance cannot be separated into 2 or more substances by physical means such as crystallization or distillation nor by mechanical means such as sifting, filtering, or using a magnet.
How can melting point be used to identify a compound?
Melting points can be used in the following way to help identify a compound. Say a sharp-melting, unknown substance X is suspected of being identical to some known substance A. If the two are identical, they should have the same melting point.
What are two ways of testing purity of a substance?
Some of the analytical purity testing methods include titration, infrared spectroscopy, paper chromatography, and optical rotation, among others. These are some of the strategies used in testing the presence of impurities in chemical compounds.
How can you predict the state of a substance?
The state of a substance at a given temperature can be predicted if its melting point and boiling point are known.
Can you use melting point to determine the identity of an unknown solid?
The melting point is a physical property of a solid and can be used to help identify a substance. For example, if an unknown solid melts at 102-106° C, the 4° range suggests that the sample is impure.
How can melting and boiling points determine the identity of a substance?
When they see a solid melt, they record the temperature as the melting point. When they see a liquid boil, they record the temperature as the boiling point. Then, you could compare their melting point to a chart of known melting points to determine their identity.
How do you determine the purity of a sample?
Percentage purity of a substance can be calculated by dividing the mass of the pure chemical by the total mass of the sample, and then multiplying this number by 100.
What is criteria of purity of solid substance?
The purity of a compound may be checked by determining its melting or boiling point. Pure solid and liquid compounds possess sharp melting and boiling points. Therefore, melting and boiling points of a compound can be used as a criteria of purity.