Acids and alkalis are solutions, and both are corrosive and only show their properties when dissolved in water, or when they are moist/wet.
To test whether a substance is acidic or alkaline, litmus papers or universal indactors are used
Properties of acid
- Has a sour taste
- pH value LESS than 7
- Turn blue litmus paper into RED
- Acid reacts with reactive metals like magnesium to produce hydrogen
- Acid reacts with carbonates to produce salt, carbon dioxides, and water.
Properties of alkali
- Has a bitter taste and a soapy feel
- pH value MORE than 7
- Turn red litmus paper into BLUE
- Alkali reacts with ammonium salts to release ammonia gas when heated
When a universal indicator has not been tested with acidic/alkaline substance or if it is tested with a neutral substance it will be green. The chart below shows the colour of the universal indicator if tested.
 |
| Above chart is the pH chart, pH0-6 are acidic,pH7 is neutral and pH8-14 is alkaline |
Neutralisation
Neutralisation is the process where an acid reacts with an alkali to form salt and water.
The salt solution produced is neutral and has a pH of 7
The GENERAL word equation for neutralisation reaction is:
Acid + Alkali -> Salt + Water
The name of the salt produced depends on the type of acid and alkali used, examples are
Sodium hydroxide(Alkali) + Hydrochloric acid(Acid) -> Sodium chloride + Water
Potassium hydroxide + Sulphuric acid -> Potassium sulphate + Water
Calcium hydroxide + Nitric acid -> Calcium nitrate + Water
Titration is used to completely neutralise an acid and an alkali.
In this method a correct volume of an acid will be added drip by drip to neutralise a volume of alkali by using a burette. The conical flask will then be shook to mix the acid and alkali evenly.
Applications of Neutralisation in Daily Life
- Vinegar(a weak acid) is used to neutralise alkaline wasp stings.
- Bicarbonate powder (a weak alkali) is used to neutralise acidic bee stings.
- Slaked lime is added to acidic soil to reduce the acidity.
Water Purification
Natural water contains impurities such as microorganisms, dissolved substances, suspended substances, decomposed substances, and silt. Water can be treated in the following ways so it can be safe to be used:
- Boiling
- Chlronation
- Filtration
- Distillation
BOILING
Boiling kills most of the microorganisms but does not remove suspended and dissolved particles and substances
CHLORINATION
Adding chlorine to water kills microorganisms but cannot remove dissolved substances. Too much chlorine in water is harmful to health too.
FILTRATION
This method removes suspended solid particles but does not remove miccroorganisms and dissolved substances.
DISTILLATION
Distilled water is pure water and is free from microorganisms, suspended particles and dissolved substances.
Water Supply System
- River water is pumped into reservoirs, mud and other suspended substances sink to the bottom.
- Water then moves through a metal screen that screens out large solid particles.
- Water is then pumped into the areation system to dissolve oxygen in the water and remove unpleasant smell.
- Water is then pumped into the coagulation tank. Alum is added to make fine solid particles stick together to form large lumps. Slaked lime is added to reduce acidity of water
- The water then flows slowly into the sedimentation tank. The large lumps of solid particles sink to the bottom.
- The water then flows into the filter tank where the remaining particles are filtered.
- In the Chlorination and fluoridation tank(replace this with disinfection in the pic, sorry), chlorine is added to kill remaining bacteria. Fluoride salt is added to prevent tooth decay
- Treated water is distributed to homes.
MUST REMEMBER THIS, MOST IMPORTANT:Coagulation-->Sedimentation-->Filtration-->Chlorination
If there are any question please leave a comment or say something at the shoutbox on the right side of this place. If you find any mistakes please do inform me because most of the information are made by my memory.
No comments:
Post a Comment