Acid-Base Titrations: Qualitative and Quantitative analysis

Primary standard

A pure, stable compound with known molar mass used to make a solution of known concentration

Equivalence point

The point in a titration where moles of acid equal moles of base

Monoprotic

An acid that donates one H⁺ ion per molecule

Diprotic

An acid that donates two H⁺ ions per molecule

Triprotic

An acid that donates three H⁺ ions per molecule

Standardization

The process of determining the exact concentration of a solution using a primary standard

weighing by difference

• typically three samples are weighed to reduce error

• use this technique to weigh multiple samples but reduce number of weighings

• initially use a top loading balance to weigh sample in a clean dry beaker

• receiving container to not need to be dry as they will not be touching the analytical balance

• weigh the sample using same procedure for analytical balance (record mass)

• remove the sample container and pour approx 1/3 or the amount of trials into the receiving container (using paper)

• place the beaker back and repeat process for last two containers

• record mass of empty weighing container

• difference in weighings is your calculated sample

• 4 masses for 3 samples

Quantitative Transfer

measure and analyze samples accurately and precisely

• Solid transfer:

  Use forceps for large chunks

  Powdered/crystallized: use weighing paper, boat, or beaker

  Weigh sample → transfer carefully → rinse container with solvent to collect all sample

• Liquid/wet transfer: Transfer solution to receiving vessel. Rinse dispensing vessel and funnel 3+ times to ensure no sample remains

Titration

accurately measure liquid volumes

Rinsing:

• Use small plastic funnel; rinse funnel with solution

• Add 5–10 mL solution, hold burette nearly horizontal and rotate to rinse inner surface

• Open stopcock to drain; repeat 2 more times

Filling & Air Removal:

• Fill near zero mark using small plastic funnel

• Open stopcock briefly to remove air bubbles from tip

• Remove funnel, wipe dry, invert on paper towel for later

Initial Reading:

• Open stopcock to slightly below zero.

• Use backing card for contrast (

• Read bottom of meniscus at eye level to 0.01 mL.

• Touch off tip droplets on clean waste beaker.

• If meniscus drops, check stopcock for leaks.

Dispensing / Titration:

• Tip 2–3 cm into flask; white background under flask.

• Swirl continuously.

• Slow down 1–2 mL from endpoint.

• Rinse inner walls to wash droplets down.

• Add drop-wise; near endpoint, use half-drops.

• Touch off droplets at tip

Clean-up:

• Pour leftover titrant into chemical waste.

• Rinse burette, stopcock, tip with hot tap water, then deionized water.

• Drain fully before storage.

Volumetric (Transfer) Pipette

• Transfers one precise volume

• Check tip for chips; bulb clean & dry.

• Rinse inside with solution, outside with water; rotate horizontally.

• Fill above mark using bulb; seal top with finger.

• Drain by gravity to mark; touch off tip do not blow out.

• Clean: hot tap → deionized water → drain.

Mohr (Graduated) Pipette

• Transfers variable volumes between graduated marks.

• Check tip and bulb.

• Rinse inside & outside; rotate horizontally.

• Fill above desired mark.

• Drain between marks only; tip is not calibrated.

• Clean same as volumetric pipette.

volumetric flask

used to prepare solutions of precise, known volume and concentration

Check for cracks or chips.

Rinse flask with deionized water before use.

For solution preparation:

Add solid or concentrated solution first.

Add solvent gradually until near calibration mark.

Mix thoroughly (invert several times) to dissolve solids completely.

Fill exactly to calibration mark at eye level; bottom of meniscus on the line.

Stopper flask and invert/mix to ensure uniform concentration.

Clean-up: rinse with tap water → deionized water → drain completely.