Q6. Three liquids are mixed together and placed into a flask. Explain how a student might separate this mixture into the individual components. Which separation technique would be best for this procedure? Which physical property does this technique rely on?

Background

Topic: Separation of Mixtures

This question tests your understanding of how mixtures can be separated based on physical properties, and which laboratory techniques are most effective for separating liquid mixtures.

Key Terms:

• Mixture: A combination of two or more substances that are not chemically bonded.

• Separation Technique: A method used to separate the components of a mixture.

• Physical Property: A characteristic such as boiling point, density, or solubility that can be used to distinguish substances.

Step-by-Step Guidance

1. Consider the physical properties of the three liquids, such as their boiling points or densities.

2. Think about common separation techniques for liquids, such as distillation or using a separatory funnel.

3. Distillation is often used when liquids have different boiling points. The liquid with the lowest boiling point will vaporize first.

4. Identify which physical property (e.g., boiling point) the chosen technique relies on.

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Q7. An alloy is found to be 21% gold (density = 19.3 g/cm3) and the rest silver (density = 10.5 g/cm3). Find the density of the alloy. Show all work.

Background

Topic: Density and Mixtures

This question tests your ability to calculate the density of a mixture (alloy) based on the densities and proportions of its components.

Key Terms and Formula:

• Density (): Mass per unit volume,

• Alloy: A mixture of two or more metals.

• Weighted Average Density:

Step-by-Step Guidance

1. Identify the fractions of gold and silver in the alloy: 21% gold and 79% silver.

2. Convert percentages to decimals: 0.21 for gold, 0.79 for silver.

3. Multiply each fraction by its respective density: for gold, for silver.

4. Add the two results to find the weighted average density of the alloy.

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Q8. An irregularly shaped piece of metal is found to have a mass of 127.8 g. When the object was placed in 40 ml of water, the water level rose to 51.39 ml. Find the density of the metal, and identify from the following: Au=19.3 g/cm3, Ag=10.5 g/cm3, Cu=8.96 g/cm3, Pb=11.2 g/cm3. Show all work.

Background

Topic: Density and Identification of Substances

This question tests your ability to calculate density using mass and volume displacement, and to identify a substance based on its density.

Key Terms and Formula:

• Density ():

• Volume Displacement: The volume of water displaced equals the volume of the object.

• Mass: g

• Volume: ml - $40 ml (or cm3)

Step-by-Step Guidance

1. Calculate the volume of the metal by subtracting the initial water volume from the final water volume.

2. Use the density formula:

3. Plug in the mass and calculated volume values.

4. Compare the calculated density to the given densities for Au, Ag, Cu, and Pb to identify the metal.

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Q9. Find the volume of an object with a mass of 271 g and a density of 7.15 g/cm3. Show work.

Background

Topic: Density Calculations

This question tests your ability to rearrange the density formula to solve for volume.

Key Terms and Formula:

• Density ():

• Volume ():

• Mass: g

• Density: g/cm3

Step-by-Step Guidance

1. Write the density formula:

2. Rearrange the formula to solve for volume:

3. Plug in the mass and density values.

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