Unit 8 Solutions

Which of the following correctly identifies 2 similarities and 3 differences between how ionic substances dissolve compared to covalent substances?

• Ionic substances dissolve in water by dissociating into ions, while covalent substances dissolve by forming hydrogen bonds. Both can dissolve in polar solvents, and both involve interactions at the molecular level.

• Ionic substances dissolve by forming hydrogen bonds, while covalent substances dissociate into ions. Both can dissolve in non-polar solvents, and both involve breaking of covalent bonds.

• Ionic substances dissolve in water by dissociating into ions, while covalent substances dissolve by forming covalent bonds. Both can dissolve in non-polar solvents, and both involve interactions at the atomic level.

• Ionic substances dissolve by dissociating into ions, while covalent substances dissolve by forming hydrogen bonds. Both can dissolve in polar solvents, and both involve interactions at the molecular level.

What type of cleaning substance would best be used to get the grease stain out? Justify your answer with reasoning.

• Dish soap

• Vinegar

• Baking soda

• Bleach

Explain how water is able to make a salt dissociate, and not just dissolve, like a sugar would.

• Water's polarity allows it to interact with the ions in salt, causing them to separate.

• Water's temperature causes salt to dissociate.

• Water's density is higher than that of salt, leading to dissociation.

• Water's pH level causes salt to dissociate.

Imagine you are in a rush out the door and only have 10 seconds to make a cup of coffee. Which of the following methods could speed up the process of mixing in your sugar and creamer to the coffee?

• Use a spoon to stir quickly

• Shake the cup gently

• Use a blender

• Let it sit for a while

Determine the molarity of a substance made from dissolving 142 g of citric acid, C6H8O7 to make 551 mL of solution.

• 0.5 M

• 1.0 M

• 1.5 M

• 2.0 M

Write 1-2 sentences to explain to someone how to make the citric acid solution.

• Mix citric acid with water until dissolved.

• Add citric acid to a solvent and stir.

• Combine citric acid with a base to form a solution.

• Heat citric acid with water to dissolve.

What mass of NaOH is dissolved in 3.6 L of a 0.045 M solution?

• 6.48 g

• 7.20 g

• 8.64 g

• 9.00 g

Ethylene glycol, C₂H₆O₂, is a common coolant used in cars. If you take your car into the shop and the mechanic fills your radiator with 8.5 kg of ethylene glycol and 1.5 kg of water dissolved into it, what is the molality of the solution?

• 1.36 mol/kg

• 91.5 mol/kg

• 33.6 mol/kg

• 4.36 mol/kg

How many grams of BaCl₂ must be added to 675 g of water in order to prepare a 1.20 molal solution?

• 34.5 grams

• 45.6 grams

• 167 grams

• 67.8 grams

List the two ways you can dilute a solution.

• Add more solvent or decrease the amount of solute

• Increase the temperature or pressure

• Add a catalyst or increase the surface area

• Use a different solvent or change the pH

Tags

NGSS.HS-PS1-5