GC: Acid-Base titrations

What is the main purpose of acid-base titrations?

• To test if reactants react.

• To calculate the concentration of unknown analyte.

• To calculate the concentration of known analyte.

• To test quality of reactants.

Answer explanation

The main purpose of acid-base titrations is to determine the concentration of an unknown analyte by reacting it with a solution of known concentration until the reaction reaches completion, indicated by a color change or pH change.

What is the role of an indicator in a reaction?

• To help reactants react successfully.

• To bind to the analyte to form a products.

• To show when the reaction has reached or past the equivalence point.

• To provide a surface for the reaction to occur.

Answer explanation

An indicator is used in a reaction to signal when the equivalence point has been reached, often by changing color. This helps determine the completion of the reaction, making it crucial for titrations and similar processes.

What is an equivalence point?

• It is the point when enough analyte has been added.

• It is the point when the amount of added titrant is equal to the amount of analyte in the solution.

• It is the point when the volume of titrant is equivalent the volume of analyte.

• It is the point when the concentration of titrant added is equivalent to the volume of analyte.

Answer explanation

The correct choice defines the equivalence point as when the amount of titrant added exactly matches the amount of analyte in the solution, indicating complete reaction. This is crucial in titration for accurate results.

what is the reading on this burette?

• 4.40mL

• 3.50mL

• 3.60mL

• 4.50mL

Answer explanation

The burette reading is determined by the bottom of the meniscus. In this case, the meniscus is at 3.60mL, making it the correct answer. The other options do not accurately reflect the meniscus position.

In a strong acid-strong base titration, what is the pH at the equivalence point?

• 7

• 1

• 10

• 5

Answer explanation

In a strong acid-strong base titration, the pH at the equivalence point is 7 because the resulting solution contains only water and neutral salts, leading to a neutral pH.

A 0.030L solution of HCl is neutralized by 0.020L of a 1.5 M NaOH solution. What is the concentration of the HCl solution?

Use the steps in your notes to help you set up this problem!

• 1.0 M

• 3.0 M

• 1.5 M

• None of the above

Answer explanation

To find the concentration of HCl, use the neutralization reaction: moles of HCl = moles of NaOH. Moles of NaOH = 0.020L * 1.5M = 0.030 moles. HCl concentration = moles/volume = 0.030 moles / 0.030L = 1.0 M.

Tags

NGSS.HS-PS1-7

A 0.150 L solution of KOH is neutralized by 0.050 L of a 0.70 M H₂SO₄ solution. What is the concentration of the KOH solution?

• 0.2 M

• 1.8 M

• 0.47 M

• None of the above

Answer explanation

To find the concentration of KOH, first calculate moles of H2SO4: 0.050 L * 0.70 M = 0.035 moles. H2SO4 neutralizes KOH in a 1:2 ratio, so moles of KOH = 0.035 * 2 = 0.070 moles. Concentration = moles/volume = 0.070 moles / 0.150 L = 0.47 M.

What is the concentration of a HCl solution if 50.0 cm³ of HCl are completely neutralized by 25.0 cm³ of a 0.50 M NaOH solution? (1 mL = 1 cm³)

• 0.250 M

• 0.500 M

• 1.00 M

• 2.00 M

Answer explanation

To find the concentration of HCl, use the neutralization reaction: moles of HCl = moles of NaOH. Moles of NaOH = 0.50 M * 0.025 L = 0.0125 moles. Since 50.0 cm³ of HCl is neutralized, concentration = 0.0125 moles / 0.050 L = 1.00 M.

If it takes 50 cm³ of 0.1 M HCl to neutralize 690 cm³ of NaOH solutions, what is the concentration of the NaOH solution?

• 0.004 M

• 0.0072 M

• 0.0036 M

Answer explanation

To find the concentration of NaOH, use the neutralization equation: M1V1 = M2V2. Here, M1 = 0.1 M, V1 = 50 cm³, and V2 = 690 cm³. Solving gives M2 = 0.0072 M, which is the concentration of the NaOH solution.

Find the pH of a solution with [OH-] = 8.41 x 10^-4.

• 3.08

• 10.92

• 9.88

• 11.23

Answer explanation

To find pH from [OH-], use pOH = -log[OH-]. Here, pOH = -log(8.41 x 10^-4) = 3.08. Then, pH = 14 - pOH = 14 - 3.08 = 10.92. Thus, the correct answer is 10.92.