U N I T 4

PH SOLUTION

ACIDS AND ALKALIS

• These are two important solutions• Not only used in

the laboratory but also in our daily life.

WHICH ONE IS ACIDIC?

ACIDS

• Comes from the Latin word ‘acidus’, which means sour.• Grapes (Tartaric Acid),

Apples (Malic Acid), Oranges, lemons (Citric Acid), Tomatoes (Salicylic Acid)• Soft drinks (carbonic

acid), car batteries (sulfuric acid)

ACID PROPERTIES

• Sour taste• Less than 7 pH• Corrosive nature:

burn skin or react with many materials• Reacts with

reactive metals

ALKALIS

• The chemical ‘opposite’ to acids.• Often used in many

household cleaners (bleach, glass cleaners, oven cleaners, detergents).• Ammonia solution,

sodium hydroxide solution, potassium hydroxide solution

ALKALI PROPERTIES

• Bitter taste• Greater than 7 pH• Soapy feel• Corrosive Nature:

reacts with ammonium salts to release ammonia when heated

ORGANIC ACIDS

INORGANIC ACIDS

DIFFERENCE BETWEEN ORGANIC & INORGANIC ACIDS

• Organic acids contain carbon, and inorganic acids don’t contain carbon.

• Generally organic acids are weaker acids than inorganic acids.

• Most of the organic acids are insoluble in water, but soluble in organic solvents. But inorganic acids are generally well soluble in water and non soluble in organic solvents.

• Organic acids have a biological origin, whereas inorganic acids haven’t. Inorganic acids are derived from inorganic compounds/mineral sources.

• Mineral acids are highly reactive with metals, and they have corrosive ability than the organic acids.

NEUTRALIZATION

• Neutralization is a process that occurs when acid reacts with alkali to form salt and water.

NEUTRALIZATION IN DAILY LIFE

• Milk of Magnesia is an alkaline serves as an antacid medicine for people suffering stomachache due to much acidity in the stomach

PH INDICATORS

• pH scale – measures how acidic or alkaline a substance is. Ranges from 0 to 14.

PH SCALE

PHENOLPHTHALEIN INDICATOR

• turns colorless when the pH of a substance is in the range of 1-8.3 or until 9, and it turns pink if the range of pH is between 10-14.

CHAPTER 5 ANSWERS

1. Solution is the end result of dissolving a substance in another substance. Suspensions are mixture containing suspended substance that are insoluble in the solvent.2. Sugar + Water → Sugar Solution3. Dilute solution, concentrated solution, saturated solution4. It is transparent and clear, the chemical and physical properties are the same throughout the solution.5. Dissolve oil from plants, give flavor to the cooked dish, remove stains from our clothes6. Solubility is the maximum amount of the solute in the grams that will dissolve in 100 g of solvent at a given temperature.7. Nature of solvent, nature of solute, and temperature

8.

solute solvent

Fragrant oil Alcohol

Ink Alcohol/acetone

Paint Turpentine

Nail polish Ethyl acetate/acetone

iodine Alcohol

9. The rate of dissolving is defined as how fast a solute dissolves in a fixed volume of solvent.10. A. The rate of dissolving increase as the rate of stirring increase. B. The rate of dissolving is slow if larger particle is used. C. An increase in temperature causes particle to dissolved faster.11. Acid is a type of solution which is in excess of hydrogen ions. Alkali is a solution that is soluble in water.12. Both acid and alkali are corrosive.13. A. Acid tastes sour whereas alkali tastes bitter. B. Acid changes the blue litmus paper red whereas alkali changes the red litmus paper to blue.

14.

Acid detergent Alkali detergent

Has pH less than 3 Has pH more than 11

Use to clean toilet Use to clean bath tub and window pane

15. Neutralization is a process that occurs when acid reacts with alkali and forms salt and water.16. Weak alkaline such as milk of magnesia can be used to relieve stomach pain which is caused by over-secretion of acid.17. pH scale, universal indicator, phenolphthalein18. Phenolpthalein turns colorless when the pH of a substance is in the range of 1-8.3 or until 9, and it turns pink if the range of pH is between 10-14.