225 Date Locker Number Name Experiment 16 Acid-Base Titrations PRELIMINARY EXERC

Question

225 Date Locker Number Name Experiment 16 Acid-Base Titrations PRELIMINARY EXERCISES: . Define the following terms associated with titrations: a. standard solution b. endpoint c. indicator 2. Write the balanced formula equation and the netionic equation for the reaction of sodium hydroxide with hydrochloric acid. Formula equation Net Ionic equation: What is the molarity of a solution prepared by dissolving 2.24 grams of NaOH in enough 3. deionized water to obtain 500.0 ml of solution? The molar mass of NaOH is 40.0 g Molarity 4. What is the color of phenolphthalein indicator in: a acidic solution b. basic solution Calculate the molarity of acetic acid in a vinegar sample, knowing that 5.00 mL of vinegar requires 43.50 mL of 0.105 M NaOH to just reach the phenolphthalein endpoint in a titration. Molarity =

Explanation / Answer

1.

Standard solution is a solution which concentration or molarity in known.

The titration of an acid with base:

The method of determine the quantity of an acid or a base by adding a calculated quantity of a base or an acid is called the titration of an acid with base.

Equivalent point:

Equivalent point is a point of acid-base titration where acid and base present in the stoichiometrically equivalent amount.

Indicator:

Indicator of acid-base titration is a compound that changes color according to pH changes of solution. In general the color of indicator of acid-base titration changes when the acidic solution becomes basic or basic solution becomes acidic.

End point:

End point of acid –base titration is a point at which the acidic solution becomes basic or basic solution becomes acidic means at this point the indicator changes its color. In general to determinate the end point we use an indicator in acid-base titration.

2.

HCl (aq) + NaOH (aq) = NaCl (aq) + H2O (l)

H+ (aq) +OH –(aq) = H2O (l)

3.

Given that   NaOH = 2.24 g

Molar mass of NaOH = 40.0 g/ mol

Volume of solution = 500.0 ml or 0.500 L

Number of mole = 2.24 g/ 40.0 g/ mole

= 0.056 mole

Molarity = number of moles / volume in L

= 0.056 Mole / 0.500 L

= 0.112 M

4. Phenolphthalein

Acids are colorless in phenolphthalein solution while bases shows pink color in phenolphthalein solution.

Acidic solution: color less

Basic solution: pink

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