Analysis of ‘cleansing power' of window cleaners
Experiment A - To determine window cleaner of which brand is the ‘best buy' by comparing the amount of NH3 and the price in different brands.
The purpose of this experiment is to determine the amount of ammonia in different brands of window cleaners by acid-base titration with hydrochloric acid.
Ammonia (NH3) is an active ingredient in window cleaners, and is alkaline in nature. Ammonia reacts with hydrochloric acid (HCl) according to the following equation:
NH3(aq) + HCl(aq) ' NH4Cl(aq)
Using methyl orange as the indicator, hydrochloric acid is titrated against window cleaner until the end-point was reached, when methyl orange turns from yellow to orange.
By equation stoichiometry, the amount of ammonia in window cleaners can be calculated, and by comparing the amount of ammonia and the price of the window cleaners, the brand of window cleaner with the lowest price per gram of ammonia is the ‘best buy'.
1. 奇偉 kiwi
2. 特惠 no frills
3. 萬"靈 glass magiclean
4. 高樂氏 Clorox
5. 奇妙 crew
1. 0.2M hydrochloric acid
2. Methyl orange
1. Stand and clamp
2. 25cm3 pipette
3. 250cm3 volumetric flask
4. 50cm3 burette
5. Conical flask
6. Filter funnel
1. Pipette 25cm3 window cleaner into a 250cm3 volumetric flask. Add deionized water to dilute the window cleaner 10 times, make the volume up to 250cm3. Mix thoroughly.
2. Pipette 25cm3 of diluted window cleaner into a conical flask.
3. Fill a clean burette with 0.2M hydrochloric acid. Record the initial burette reading.
4. Add 3 drops of methyl orange solution to the conical flask.
5. Run hydrochloric acid from the burette into the conical flask while swirling. Stop when the solution turns from yellow to orange. Record the final burette reading.
6. Repeat steps 2-5 a few times until the results are consistent.