AP Chem titration calculations cheat sheet

What is a titration?

A titration is a laboratory method used to determine the concentration of a solution by reacting it with a standard solution.

Define endpoint in titration.

The endpoint is the point in a titration at which the indicator changes color, signaling that the reaction is complete.

True or False: Titration measures volume only.

False. Titration measures both volume and concentration to determine unknowns.

What is a standard solution?

A standard solution is a solution with a known concentration, used to determine the concentration of an unknown solution.

Fill in the blank: The _______ curve shows pH changes during a titration.

titration curve.

Compare strong acid vs. weak acid titration curves.

Strong acids show a sharp pH change at the equivalence point; weak acids have a more gradual slope.

What role does an indicator play?

An indicator signals the endpoint of a titration by changing color at a specific pH range.

Cause → Effect: Adding NaOH to HCl during titration?

Causes pH to increase until neutralization is reached.

What is the purpose of a burette?

A burette delivers precise volumes of titrant during a titration, ensuring accuracy.

Calculate molarity: 0.1 M NaOH in 50 mL. What is moles?

Moles = Molarity × Volume = 0.1 mol/L × 0.050 L = 0.005 moles.

True or False: Titration can be done without an indicator.

True. However, it is less precise without an indicator to determine the endpoint.

What is the equivalence point?

The equivalence point is when the quantities of acid and base are stoichiometrically equivalent.

Define molarity.

Molarity (M) is the number of moles of solute per liter of solution. \( M = \\frac{\text{moles of solute}}{\text{liters of solution}} \)

Calculate molarity of 1 mole in 2L solution.

M = 1 mol / 2 L = 0.5 M

True or False: Dilution increases concentration.

False. Dilution decreases concentration by adding solvent, thus reducing solute per volume.

Fill in the blank: The formula for dilution is _____.

M₁V₁ = M₂V₂ - where M is molarity and V is volume.

If you dilute 3M solution to 1L, what is the new volume?

Use M₁V₁ = M₂V₂: 3M x V₁ = 1M x 1L → V₁ = 0.33L.

Concentration change during a titration depends on _____.

The stoichiometry of the reaction and the volumes of titrant and analyte used.

What happens when you add more titrant?

The concentration of the analyte decreases, and the reaction shifts until neutralization.

Calculate final concentration: 0.5M NaCl diluted to 500mL.

Use M₁V₁ = M₂V₂: 0.5M x 250mL = M₂ x 500mL → M₂ = 0.25M.

What is the effect of temperature on molarity?

Molarity may change with temperature due to volume expansion of the solvent.

Compare molarity and molality.

Molarity is moles per liter of solution; molality is moles per kg of solvent.

Calculate moles in 0.75M solution with 2L.

Moles = M × V = 0.75M × 2L = 1.5 moles.

What is the concentration change at equivalence point?

At equivalence point, the moles of titrant equal the moles of analyte; concentration can be calculated using stoichiometry.

Mole ratio in titrations

The ratio of moles of reactants based on the balanced equation. Use it for stoichiometric calculations.

What is the endpoint?

The point in a titration where the indicator changes color, indicating complete reaction.

True or False: Titration requires a balanced equation.

True. A balanced equation is essential for accurate stoichiometric calculations.

Calculate moles of NaOH needed: 0.1 M, 50 mL HCl.

Moles HCl = 0.1 M × 0.050 L = 0.005 moles. NaOH also needs 0.005 moles (1:1 ratio).

Difference between titrant and analyte?

Titrant: solution of known concentration; Analyte: solution of unknown concentration being analyzed.

Fill in the blank: Moles = ____ × Volume.

Moles = Molarity × Volume in liters.

What is dilution?

The process of reducing the concentration of a solution by adding more solvent.

Stoichiometry formula for titration: __ = __.

Moles of acid × volume of acid = Moles of base × volume of base.

Cause of color change in titrations?

The reaction between the titrant and analyte causes the indicator to change color at the endpoint.

What is a primary standard?

A pure substance that can be used to determine the concentration of a solution accurately.

Titration curve: what does it show?

It shows pH changes as titrant is added, indicating the strength and equivalence point of the acid/base.

What is the significance of the equivalence point?

The point at which the amount of titrant equals the amount of substance being titrated, indicating complete reaction.

What is an indicator in titrations?

A chemical that changes color at a specific pH range, signaling the endpoint of a titration.

True or False: All indicators are universal.

False. Different indicators have different pH ranges and are suitable for specific types of titrations.

Identify a common acid-base indicator.

Phenolphthalein: Turns from colorless to pink at pH 8.2 to 10.

What color change indicates endpoint with methyl orange?

Changes from red in acid to yellow in neutral to alkaline solutions.

Fill in the blank: The endpoint is the point at which ______.

The amount of titrant added is stoichiometrically equivalent to the analyte.

Compare bromothymol blue and phenolphthalein.

- Bromothymol blue: pH range 6.0-7.6, yellow to blue. - Phenolphthalein: pH range 8.2-10, colorless to pink.

Cause → Effect: What happens if the wrong indicator is used?

The endpoint may be misidentified, leading to inaccurate titration results.

How to visually identify the endpoint?

Observe a permanent color change in the solution when adding the titrant.

What is the pH range of universal indicator?

Approximately pH 4 to 10, showing a gradient of colors.

What characteristic makes an indicator suitable for a titration?

Must change color at or near the equivalence point of the titration.

Example: Calculate pH at endpoint for strong acid-strong base.

pH = 7, at the equivalence point of titration.

What does a color change above the endpoint indicate?

It suggests excess titrant has been added, potentially leading to an inaccurate measurement.