Experiment #8: Acids and Bases

Hydrogen ion (H⁺) or proton

Hydrogen ion (H⁺) or proton

The ion responsible for the common properties of acids

Hydroxide ion (OH^-)

The ion responsible for the common properties of bases

hydronium ion (H₃O⁺)

When hydrogen ion is hydrated becomes

Arrhenius definition

A way to define acids and bases based on the concentration of either hydrogen and hydroxide ions present when dissolved in water.

titration

A way to determine the measurement of the volume of a base or acid of known concentration required to neutralize it.

equivalence point

it is a point when the number of moles of the base is stoichiometrically equivalent to the number of moles of the base.

endpoint

The point at which the chemical indicator changes color, which is also the experimental estimation of the equivalence point.

1. Touch a drop of NaOH. Note

2. Test 1 ml each of the ff. using red and blue litmus paper, phenolphthalein and methyl orange indicator.

   • Dilute HCl

   • Dilute NaOH

   • NaCl solution

   • Vinegar

   • Soap solution

   • Calamansi juice

   • Dilute HNO3

   • Dilute CH3COOH

   • Dilute H2SO4

   • Dilute H3PO4

   • Potassium Acetate

Steps involved in A. Tests for acids and bases

1. Clean a base buret. Rinsed with distilled water.

2. Hold over a beaker to catch the base flow. Rinse with 3 successive 5ml of standard 0.1N NaOH. Fill up to the near zero mark with the base. Open pinchcock to allow the base to flow down until no air bubble is left. Record initial volume

3. Pipet 5 ml of vinegar into a 125 ml Erlenmeyer flask and add 5 drops of phenolphthalein indicator

4. Add 0.1N NaOH solution to the acid slowly, swirling the flask, until a light pink color lasts for a minute. Endpoint. Record final reading.

5. Compute for the M of acetic acid in the vinegar.

Steps involved in A. Acid-base neutralization by Titration

1. Get the volume of the titrant:
   Volume of titrant = Final reading - initial reading

2. Get the molarity of titrand:

   Molarity of titrand = (Volume fo titrant)(Molarity of titrant)(mol of titrand/mol of titrant) divided by mL sample

How to compute for Molarity?

 sour with faintly bitter taste

Taste of dilute HCl

initially bitter with a slight stingy sensation, then becomes soapy

Taste of dilute NaOH

slippery

Feeling of dilute NaOH to the touch

NaOH, soap solution, and potassium acetate - basic solutions

Data and Results: Which reagents turned the red litmus paper to blue?

HCl, vinegar, Calamansi juice, Dilute HNO3, HAc, H2SO4, and H3PO4 solution - acidic solutions

Data and Results: Which reagents turned the blue litmus paper to red?

NaCl solution - neutral

Data and Results: Which reagent did not have any reaction to the red and blue litmus paper?

NaOH, soap solution, and potassium acetate - basic solutions

Data and Results: Which reagents turned pink when added with phenolphthalein indicator?

HCl, vinegar, Calamansi juice, Dilute HNO3, HAc, H2SO4, and H3PO4 solution (acidic solutions) and NaCl solution (neutral)

Data and Results: Which reagents remained colorless when added with phenolphthalein indicator?

NaCl solution - neutral

Data and Results: Which reagents remained orange when added with methyl orange indicator?

NaOH, soap solution, and potassium acetate - basic solutions

Data and Results: Which solutions turned yellow when added with methyl orange indicator?

HCl, vinegar, Calamansi juice, Dilute HNO3, HAc, H2SO4, and H3PO4 solution (acidic solutions)

Data and Results: Which solutions turned red when added with methyl orange indicator?

Molarity is simply how many moles of the solute there are per liter of solution. It can be expressed as M or Mol/L.

How will you define molarity?

Sodium bicarbonate or baking soda (NaHCO₃), has a unique ability to function as both an acid and a base. This dual nature makes it an amphiprotic substance.

Why can NaHCO3 neutralize acids or bases if each one is spilled on the skin?