Q1. What is the molarity of a solution prepared by dissolving 10.19 g of ethanol (CH3CH2OH) in enough water to produce 250.0 mL of solution?

Background

Topic: Solution Concentration (Molarity)

This question tests your ability to calculate molarity, which is a measure of the concentration of a solute in a solution.

Key Terms and Formulas:

• Molarity ():

• Moles:

• Molar mass of ethanol (): Calculate using atomic masses.

Step-by-Step Guidance

1. Calculate the molar mass of ethanol (): Add up the atomic masses for C, H, and O.

2. Find the number of moles of ethanol:

3. Convert the volume of solution from mL to L:

4. Set up the molarity formula:

Try solving on your own before revealing the answer!

Q2. What is the mass of chloride ions in a 375 mL of a 0.250 M solution of magnesium chloride?

Background

Topic: Solution Stoichiometry

This question tests your ability to calculate the mass of ions in a solution, using molarity and stoichiometry.

Key Terms and Formulas:

• Molarity ():

• Magnesium chloride formula:

• Stoichiometry: Each mole of gives 2 moles of

• Mass:

Step-by-Step Guidance

1. Convert 375 mL to liters:

2. Calculate moles of :

3. Determine moles of : Multiply moles of by 2.

4. Calculate mass of :

Try solving on your own before revealing the answer!

Q3. What volume of a 2.00 M stock solution of NaOH is required to prepare 50.0 mL of a 0.400 M solution of NaOH?

Background

Topic: Solution Dilution

This question tests your ability to use the dilution equation to prepare a solution of desired concentration.

Key Terms and Formulas:

• Dilution equation:

• = initial (stock) molarity, = volume of stock solution

• = final molarity, = final volume

Step-by-Step Guidance

1. Identify the known values: , ,

2. Set up the dilution equation:

3. Rearrange to solve for :

4. Plug in the values, but do not calculate the final volume yet.

Try solving on your own before revealing the answer!

Q4. What volume of 0.250 M HCl is needed to react completely with 25.00 mL of 0.375 M Na2CO3?

Background

Topic: Stoichiometry of Acid-Base Reactions

This question tests your ability to use stoichiometry and molarity to determine the volume of one reactant needed to react with another.

Key Terms and Formulas:

• Balanced equation:

• Moles: (with V in liters)

• Stoichiometry: 1 mole reacts with 2 moles

Step-by-Step Guidance

1. Calculate moles of :

2. Use stoichiometry to find moles of needed: Multiply moles of by 2.

3. Set up the equation for volume of :

4. Leave the calculation for the student to complete.

Try solving on your own before revealing the answer!

Q5. The concentration of a KMnO4 solution can be determined by titration with a known amount of oxalic acid, H2C2O4, according to the following reaction:

5H2C2O4(aq) + 2 KMnO4(aq) + 3H2SO4(aq) → 10 CO2 (g) + 2 MnSO4(aq) + K2SO4(aq) + 8 H2O(l)

What is the concentration of KMnO4 solution if 22.35 mL reacts with 0.5170 g of oxalic acid?

Background

Topic: Titration and Redox Stoichiometry

This question tests your ability to use titration data and stoichiometry to determine the concentration of a solution.

Key Terms and Formulas:

• Moles:

• Stoichiometry: 5 moles react with 2 moles

• Molarity:

Step-by-Step Guidance

1. Calculate the molar mass of oxalic acid ().

2. Find moles of oxalic acid:

3. Use the reaction stoichiometry to find moles of that reacted.

4. Convert 22.35 mL to liters:

5. Set up the molarity formula for :

Try solving on your own before revealing the answer!

Q6. Balance the following redox reactions under acidic conditions:

Background

Topic: Redox Reaction Balancing

This question tests your ability to balance redox reactions using the half-reaction method, both in acidic and basic solutions.

Key Terms and Formulas:

• Half-reaction method: Split into oxidation and reduction, balance atoms, electrons, and add or as needed.

• In acidic solution: Use and to balance.

• In basic solution: Use and to balance.

Step-by-Step Guidance

1. For each reaction, identify oxidation and reduction half-reactions.

2. Balance all atoms except H and O.

3. Balance O by adding , then H by adding (acidic) or (basic).

4. Balance charge by adding electrons.

5. Combine half-reactions and check overall balance.

6. For basic solution, add to both sides to neutralize and form .

Try balancing on your own before revealing the answer!