Elements, compounds and mixtures：练习题

Which mixture can be separated into its components using the technique of filtration?

A student performs a chromatography experiment. The solvent front moves \(12.0 \text{ cm}\) and a red dye moves \(4.8 \text{ cm}\). What is the \(R_f\) value of the red dye?

A chromatogram is obtained for an unknown food dye. It shows three distinct spots at different heights from the baseline. One of the spots aligns perfectly with the spot of a known banned additive. Which conclusion is most accurate?

Which of the following best defines a compound in chemical terms?

A student performs paper chromatography on a dye. The solvent front moves a distance of \( 15.0\text{ cm} \) from the baseline. If the component has an \( R_f \) value of \( 0.64 \), what is the distance moved by the spot from the baseline?

Classify the following substances as an element, a compound, or a mixture:
i) Magnesium ribbon
ii) Carbon dioxide gas

In a paper chromatography experiment, explain why it is essential that the level of the solvent is below the baseline where the spots are placed.

In a chromatography experiment, if a substance is insoluble in the chosen solvent, where will the spot be located on the final chromatogram?

Substances can be classified into different categories based on their composition.

a) Define the term solvent.

b) A student has a mixture of sand and water. Explain why filtration is a suitable method to separate the sand from the water.

c) A different mixture contains sodium chloride dissolved in water. Name the experimental technique used to obtain pure water from this mixture.

Substances can be classified as elements, compounds, or mixtures.

a) For each of the following, state whether it is an element, a compound, or a mixture:

i) Air
ii) Distilled water
iii) Oxygen gas
iv) Salt dissolved in water

b) Describe how you would separate a mixture of sand and iron filings, explaining the principle behind the chosen method.