ACID,BASE AND SALT By IIN INDRIYATI Biology Teacher of SMP 1 Wonosari
A. Competence Standard : 5. To understand the characteristic of acid, base and salt B. Basic Competence : 5.1 To identify the characteristic of acid, base and salt byusing accurate tools and indicators • Objective : 1. Student able to identify the characteristic of acid, base and salt after do experiment
ACID • Acid is a substance that releases hydrogen ion ( H+) when it’s dissolved in water and a negative ion will be formed according to the following reaction : • Acid H+ + negative ion example : HCl H+ + Cl – (Hydrochloric acid) H2SO4 2H+ + SO42- (Sulfuric acid)
Acid characteristics • There are corosive, meaning they can destroy other materials including metal, marble, • They have sour taste • They can conduct electricity. • They can change blue litmus to red • They have a pH of less than 7
Acids Affect Indicators, by changing their color Blue litmus paper turns red in contact with an acid (and red paper stays red).
Matters that contain acid • Lemon • Tomato • Vinegar • Manggo • Starfruit • etc
Strong Acids • Strong acids are very corrosive. They react with metals and can cause severe burns on the skin. They conduct electricity well. • Strong acids: Hydrochloric HCl Nitric HNO3 Sulfuric H2SO4 HydrobromicHBr
Base • Base is substance that releases hydroxide ion (OH-) when it’s dissolved in water and positive ions are formed according to the following reaction • Base positive ion + OH- • Example : NaOH Na+ + OH- Sodium hydroxide NH4OH NH4+ + OH- Ammonium hydroxide
Base characteristics • They caustic, meaning they can damage our skin or other materials • They feel smooth on our hand • They have bitter taste • They can change red litmus to blue
Bases Affect Indicators Red litmus paper turns blue in contact with a base (and blue paper stays blue). Phenolphthalein turns purple in a base.
Bases Neutralize Acids Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl. 2 HCl + Mg(OH)2 Magnesium salts can cause diarrhea (thus they are used as a laxative) and may also cause kidney stones. MgCl2 + 2 H2O
Matters that contain base • Soap • Detergent • Thootpaste • Baking soda • Stomach medicine/ Antasid (obat perut) • etc
Common Bases • Sodium hydroxide NaOH • Calcium hydroxide Ca(OH)2 • Magnesium hydroxide Mg(OH)2 • Ammonium hydroxide NH4OH
SALT • Salt is formed by reaction between acid and base • The reaction between Acid and Base is called the neutralization reaction • Acid + Base Salt + Water • Example : NaCl • HCl (asam) + NaOH (basa) --------- NaCl (garam dapur) + H2O (air)
Measuring pH • Why measure pH? • Everyday solutions we use - everything from swimming pools, soil conditions for plants, medical diagnosis, soaps and shampoos, etc. • Sometimes we can use indicators, other times we might need a pH meter
How to measure pH with wide-range paper 1. Moisten the pH indicator paper strip with a few drops of solution, by using a stirring rod. 2.Compare the color to the chart on the vial – then read the pH value.
Artificial indicators : - Lithmus paper - Universal indicator - Phenolphthalein - Red methil - Blue bromthymol Natural indicators : - Hibiscus - Turmeric - Red cabbage - Mangosteen Acid – Base Indicators
Thank’s you • See you next time • Good by