Pre-AP Chemistry Solutions

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Questions and Answers

What type of solution is created when 100g of NH3 is dissolved in 150 mL of water at 25°C, and how do you know?

A basic solution, as NH3 is a base. This is known because NH3 is a weak base and accepts H+ ions, increasing the pH of the solution.

What is the purpose of cooling a saturated solution of KNO3 from 65°C to 35°C, and what will happen as a result?

The purpose is to create a supersaturated solution. As a result, precipitate will form as the solubility of KNO3 decreases with decreasing temperature.

What is the relationship between pH and pOH in a solution, and why is it significant?

pH + pOH = 14, which is significant because it allows us to calculate one value if the other is known, as they are inversely related.

What is the conjugate acid-base pair in the reaction HBr(aq) + H2O(l) -> H3O(aq) + Br(aq), and what does this imply?

The conjugate acid-base pair is H3O+/Br-, implying that HBr is a strong acid and completely dissociates in water. Signup and view all the answers

What is the purpose of titration in calculating the concentration of an acid or base, and how is it achieved?

The purpose of titration is to determine the concentration of an acid or base by reacting it with a known volume and concentration of a strong acid or base. Signup and view all the answers

A student needs to prepare 250.0 mL of a 0.050 M solution of potassium phosphate. Describe the procedure to prepare this solution from a 5.00 M stock solution, specifying the volume of the stock solution required.

To prepare 250.0 mL of a 0.050 M solution of potassium phosphate, the student needs to dilute the 5.00 M stock solution. The volume of the stock solution required can be calculated as follows: volume of stock solution = (desired volume) x (desired concentration) / (stock concentration) = 250.0 mL x 0.050 M / 5.00 M = 2.50 mL. Therefore, the student needs to take 2.50 mL of the 5.00 M stock solution and dilute it with water to a final volume of 250.0 mL. Signup and view all the answers

In the reaction HNO2(aq) + H2O(l) -> H3O(aq) + NO2(aq), what are the conjugate acid-base pairs?

The conjugate acid-base pairs are HNO2 (acid) and NO2- (conjugate base), and H3O+ (conjugate acid) and H2O (base). Signup and view all the answers

A solution of HBr is created by dissolving 120g into 150 mL of water at 25°C. What type of solution is this and how do you know?

This is a saturated solution. The student knows this because the amount of HBr dissolved is greater than the solubility of HBr in water at 25°C. Signup and view all the answers

A saturated solution of KOH is made with 1.75L of water at 85°C and cooled to 35°C. Assuming a supersaturated solution is not created, how much precipitate will form?

To find the amount of precipitate, the student needs to find the solubility of KOH at 35°C and subtract it from the initial amount of KOH dissolved at 85°C. The difference will be the amount of precipitate formed. Signup and view all the answers

What mass of Ca(OH)2 would be required to make 305 mL of a 0.66M solution?

The student needs to calculate the number of moles of Ca(OH)2 required and then multiply it by the molar mass of Ca(OH)2. moles = (volume) x (concentration) = 0.305 L x 0.66 M = 0.201 mol. mass = moles x molar mass = 0.201 mol x 74.1 g/mol = 14.9 g. Signup and view all the answers

Study Notes

Pre-ap Solutions

pH is calculated as -log[H+]
pOH is calculated as -log[OH-]
pH + pOH = 14

Solutions and Stoichiometry

A solution of NH3 created by dissolving 100g into 150 mL of water at 25°C is an unsaturated solution.
A saturated solution of KNO3 made with 1.75L of water at 65°C and cooled to 35°C will form precipitate.
To make a saturated solution of ammonium chloride, the student needs to add a certain amount of ammonium chloride to 220 mL of water at 30°C with a concentration of 0.45g/mL.
To make 302 mL of 0.66M K2SO4 solution, a certain mass of K2SO4 is required.

Stoichiometry Solutions

To completely neutralize 45.65μL of sulfuric acid, a certain volume of 0.889mM magnesium hydroxide is required.
The resulting solution will have a certain molar concentration of magnesium sulfate.
To make 125.0mL of a 25.0mM solution of sodium phosphate, the student needs to dilute a certain amount of 7.00M stock solution.
HBr(aq) and H3O(aq) are conjugate acid/base pairs.
To titrate 25.0 mL of a solution containing H3PO4, a certain volume of 0.500 M NaOH is required.
To neutralize 50.0 mL of 0.45 M hydrobromic acid, a certain volume of 0.750M potassium hydroxide is required.

Stoichiometry Solutions (continued)

To completely neutralize 30.5 μL of hydrochloric acid, a certain volume of 1.25 mM calcium hydroxide is required.
The resulting solution will have a certain molar concentration of aluminum sulfate.
To make 150.0mL of a 30.0mM solution of potassium phosphate, the student needs to dilute a certain amount of 5.00M stock solution.
HNO2(aq) and H3O(aq) are conjugate acid/base pairs.
To titrate 35.0 mL of a solution containing H2SO4, a certain volume of 0.750 M KOH is required.
To neutralize 60.0 mL of 0.60 M hydroiodic acid, a certain volume of 1.0M sodium hydroxide is required.

Solubility and Saturation

A solution of HBr created by dissolving 120g into 150 mL of water at 25°C is an unsaturated solution.
A saturated solution of KOH made with 1.75L of water at 85°C and cooled to 35°C will form precipitate.
To make a saturated solution of lithium chloride, the student needs to add a certain amount of lithium chloride to 220 mL of water at 30°C with a concentration of 0.55g/mL.
To make 305 mL of 0.66M Ca(OH)2 solution, a certain mass of Ca(OH)2 is required.
To make a certain volume of 1.5 M glucose solution, a certain mass of glucose is required.
To combust 360mL of a 1.5M solution of sucrose, a certain mass of oxygen is required.

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Description

Quiz on chemistry solutions, including types of solutions, dissolving, concentration, and precipitation. Problems involve calculating concentrations, precipitates, and solution properties.