AP Chem 3.7-3.10

The substance that does the dissolving

• Solute

• Solvent

• Solution

• Miscibility

Tags

SPQ-3.C

Which of the following would be the MOST soluble in water?

• CH₄

• CO₂

• NH₃

• C₂H₆

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SPQ-3.C

2.45 mole of LiBr is dissolved to make a 0.750 L of solution. What is the molarity?

• 3.27 M

• 0.306 M

• 0.0376 M

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SPQ-3.A

How many grams of CaCl₂ are needed to prepare 125 ml of a 0.500 M solution?

• 4.00 g

• 6936 g

• 6.94 g

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SPQ-3.A

How many moles of NH₃ are in a 3.0 L solution of a 0.23 M NH₃.

• 0.69 mol

• 13 mol

• 0.077 mol

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SPQ-3.A

Solid Al(NO₃)₃ is added to distilled water to produce a solution in which the concentration of nitrate, [NO₃^-], is 0.10 M. What is the concentration of aluminum ion, [Al³⁺], in this solution?

• 0.010 M

• 0.033 M

• 0.066 M

• 0.10 M

• 0.30 M

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SPQ-3.A

Which of the following questions about the components in a mixture could be investigated with a paper chromatography experiment?

• Do the components have different densities?

• Do the components have different molecular masses?

• Do the components have different molecular polarities?

• Do the components have different average molecular speeds?

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SPQ-3.C

Which of the following is the best piece of laboratory glassware for preparing 500.0 mL of an aqueous solution of a solid?

• Volumetric flask

• Erlenmeyer flask

• Test tube

• Graduated beaker

• Graduated cylinder

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SPQ-3.A

An ionic crystal is added to water and starts to dissolve as shown in the particulate representation above. Based on the orientation of the water molecules, what can be assumed about the charge of the hydrated particle indicated by the arrow?

• The particle is positively charged, because the oxygen atoms in water are attracted to it.

• The particle is negatively charged, because hydrogen atoms in water are attracted to it.

• The particle is both positively and negatively charged, because the water molecules are attracted to it.

• The particle is neutral, because the dipoles of the water molecules neutralize the charge of the particle.

Answer explanation

The oxygen atom of a water molecule has a partial negative charge due to oxygen’s greater electronegativity compared to hydrogen. The negative oxygen in H2O is attracted to positive particles (e.g., cations). The diagram shows the oxygen atoms of water molecules next to the particle indicated by the arrow, indicating that it has a positive charge.

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SPQ-3.B

The diagram above shows a thin-layer chromatogram of a mixture of products from a chemical reaction. The separation was performed using 50% ethyl acetate in hexane as the solvent (mobile phase) and silica gel as the polar stationary phase. On the basis of the chromatogram and the information about solvents in the table above, which of the following would be the best way to decrease the distance that the products travel up the plate?

• Use pentane instead of hexane in the solvent.

• Decrease the percentage of ethyl acetate in the solvent.

• Increase the percentage of ethyl acetate in the solvent.

• Add up to 5% methanol to the solvent.

Answer explanation

To decrease the distance that the products move up the plate, the relative affinity of the products for the solvent should be decreased. This can be accomplished by decreasing the percentage of the ethyl acetate in the solvent.

Tags

SPQ-3.C