Acids and bases can be identified by their names or chemical formulas. Acids contain hydrogen (H) or a carboxyl group (COOH) and have a pH below 7. Bases contain a metallic or ammonium ion and hydroxide (OH) and have a pH above 7. Acid-base indicators change color at specific pH levels and can be used to determine if a solution is acidic or basic. A neutralization reaction occurs between an acid and base, producing water and a salt.

1. ACIDS & BASES

2. ACIDS You can identify an acid from its name or chemical formula Usually the name of an acid ends with the word “ acid ”

3. If you are given the chemical formula of a substance, you know it is an acid if: the chemical formula starts with “ H ” OR the chemical formula ends with “ COOH ” ( carboxyl group ) ACIDS

4. For example: HF (aq) is an acid because it starts with H Hydrofluoric acid is used for etching glass CH 3 COOH (aq) is an acid because it ends with COOH The name of this acid is “ acetic acid ” Diluted acetic acid is vinegar ACIDS

5. NAMING ACIDS When the chemical formula of an acid starts with H and only contains one other non-metallic element, it is named as follows:

6. Step 1: Start with the prefix “ hydro ” Step 2: take the first part of the non-metallic element and add the suffix “ ic ” and the word “ acid ” ex.) HCl(aq) = “ hydrochloric acid ” HF(aq) = “ hydrofluoric acid ” NAMING ACIDS

7. Sometimes the chemical formula of an acid contains a polyatomic ion For example, H 2 SO 4 (aq) contains the polyatomic ion sulphate ( SO 4 2- ) When naming an acid containing a polyatomic ion, do the following: NAMING ACIDS

8. Step 1: Start with the name of the element in the polyatomic ion that is not oxygen Step 2: Add the suffix “ ic ” and the word “ acid ” ex.) H 2 SO 4 (aq) = sulphuric acid H 3 PO 4 (aq) = phosphoric acid NAMING ACIDS

9. BASES Bases can also be identified from their name or chemical formula A substance is a base if its name begins with the name of a metallic ion and ends with the word “ hydroxide ”

10. A substance is also a base if: the chemical formula starts with a metallic ion or with the ammonium ion NH 4 + AND the chemical formula ends with OH ( hydroxyl group) BASES

11. For example, NaOH (s) starts with the metallic ion sodium ( Na + ) and ends with OH - Similarly, KOH (s) starts with the metallic ion potassium ( K + ) and ends with OH - NH 4 OH starts with the ammonium ion NH 4 + and ends with OH - BASES

12. NAMING BASES Step 1: write the name of the positively charged ion Step 2 : Add the word “ hydroxide ” ex.) KOH = potassium hydroxide NH 4 OH = ammonium hydroxide

13. ACIDS & BASES Thousands of years ago, scientists used taste to distinguish acids from bases Acids taste sour and bases taste bitter Tasting unknown substances is not a safe way of identifying it or its properties

14. pH Today you can determine if a substance is an acid or a base by measuring its pH The pH measurement is related to the number of hydrogen ions ( H + ) that are in a solution The abbreviation “pH” stands for “ power of hydrogen ”

15. The pH scale is a number scale that indicates how acidic or basic a solution is The pH of a substance can only be determined when it is in aqueous solution (dissolved in water ) pH

16. Pure water has a pH of 7 Any substance with a pH of 7 when it is in aqueous solution is neutral A neutral substance is neither an acid nor a base pH

17. An acid is a substance that has a pH of less than 7 when it is in aqueous solution The more acidic a substance is, the lower the pH pH

18. A base is a substance that has a pH greater than 7 when it is in aqueous solution The more basic a substance is, the higher the pH pH

19. pH

20. One unit of change on the pH scale represents a change by a factor of 10 in how acidic or basic a solution is ex.) stomach acid has a pH of 1 . This is 10 times more acidic than lemon juice, which has a pH of 2 . pH

21. Acid-Base Indicators An acid-base indicator is any substance that changes colour in the presence of an acid or a base The most widely known acid-base indicator is litmus

22. Litmus is a plant extract that can be blue or red (pink) Litmus turns red/pink in an acidic solution Litmus turns blue in a basic solution Acid-Base Indicators

23. The colour of hydrangea flowers is dependent upon the pH of the soil Acid-Base Indicators

24. It would be impossible to determine the pH of all solutions using just one indicator, such as litmus Several other acid-base indicators exist, each producing a colour change at a specific pH level Acid-Base Indicators

26. A universal indicator is a mixture of chemicals that changes colour through a wide range of pH values Acid-Base Indicators

27. An even more precise way of determining pH is to use a pH meter

28. Properties of Acids & Bases Similarities : dissolve in water conduct electricity in aqueous solution can irritate or burn skin

29. Differences : BASES ACIDS turn litmus blue turn litmus red/pink do not react with metals to produce a compound and hydrogen gas react with metals to produce a compound and hydrogen gas do not corrode metals corrode metals release hydroxide ( OH - ) ions in aqueous solution release hydrogen ( H + ) ions in aqueous solution pH > 7 pH < 7 feel slippery do not feel slippery taste bitter taste sour

30. Neutralization Reactions Neutralization is a chemical reaction between an acid and a base that produces water (H 2 O) and a salt acid + base  salt + water

31. The salts formed may be soluble in water or can be insoluble If the salt is insoluble, a precipitate will form Recall: a precipitate is a suspension of small, solid particles formed during a chemical reaction Neutralization Reactions

32. Applications of neutralization reactions: Pharmaceuticals Agriculture Food industry Neutralization Reactions