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Acids, bases, and pH. Objectives Describe the ionization of strong acids in water and the DISSOCIATION of strong BASES in water Distinguish between solutions.

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Presentation on theme: "Acids, bases, and pH. Objectives Describe the ionization of strong acids in water and the DISSOCIATION of strong BASES in water Distinguish between solutions."— Presentation transcript:

1 Acids, bases, and pH

2 Objectives Describe the ionization of strong acids in water and the DISSOCIATION of strong BASES in water Distinguish between solutions of weak acids or bases and strong acids or bases Relate pH to the concentration of HYDRONIUM ions in a solution

3 What are acids

4 ACIDS Acid – any compound that INCREASES the number of HYDRONIUM ions when dissolved in water Example : H 2 O + HCl  H 3 O + + Cl - Acids will IONIZE in water = form ions see above example Acids will turn BLUE litmus paper RED

5 Common acids Common examples of acids – citrus fruits Formic acid – an acid found in stinging ants HCOOH Vinegar = acetic acid CH 3 COOH Hydrochloric acid – HCl Nitric acid HNO 3

6 Acids IONIZE When an acid is dissolved in water the Hydrogen from the acid forms a bond with a water molecule to form a HYDRONIUM ION and the anion from the acid Example : H 2 O + HCL  H 3 O + + Cl - H 2 O + CH 3 COOH  H 3 O + + CH 3 COO -  A double arrow in an equation indicates that the reaction goes in both directions

7 Weak acids DO NOT ionize completely A double arrow indicates that the ions quickly go back to the original acid and water Weak acids are POOR ELECTROLYTES A STRONG acid DOES ionize completely indicated by a single arrow Strong acids are GREAT ELECTROLYTES

8 STRONG ACIDS conduct electricty = Electrolyte – a light bulb will glow brightly

9 Weak Acids are POOR Electrolytes A light bulb will BARELY glow

10 Indicators A compound that can reversibly change color depending on the pH of the solution Litmus paper – Identifies if a solution is an acid or a base An acid turns blue litmus paper RED A base turns red litmus paper blue pH paper – will determine the pH of the solution from a range of pH1(strong acid) red through pH14 (strong base) blue

11 Acids are dangerous in concentrated form Concentrated acids damage human tissue Acetic acid = vinegar sold in 5% solution b/c concentrated acetic acid(glacial) damages tissue and the vapors damage tissues of the eyes, mouth, lungs Stomach acid = pH 2 which damages tissue outside of the stomach – when a person “throwsup” the mucus lining of their throat and nose is “burned”

12

13 BASES Any compound that increases the number of HYDROXIDE ions when dissolved in water Example: Strong bases NaOH + H 2 O  Na + + OH - + H 2 O KOH + H 2 O  K + +OH - + H 2 O Strong ELECTROLYTES

14 WEAK BASES Do minimally increase the OH - Do not dissociate completely in water The water acts like an ACID by donating the hydrogen ion NH 3 + H 2 O  NH OH -  Ammonia becomes ammonium ion

15 CH 3 NH 2 + H 2 O  CH 3 NH OH -  Just as in the weak acid the “double arrow” in the equation means the reaction is going in both directions Weak Electrolyte – since the ions form and then reform into noncharged molecules again

16 pH scale NewSiteImages2011/phscalergb.jpghttp://www.alternativemedicinedirect.com/ NewSiteImages2011/phscalergb.jpg

17 pH power of hydronium A value used to express the acidity or alkalinity(base) of a solution Negative logarithm Logarithm = exponent Example: If the concentration of H 3 O + = 1x10 -2 The exponent = -2 The “NEGATIVE” of -2 = 2 The pH then =2

18 WATER

19 Because water dissociates the concentration of H 3 O + equals the concentration of OH - The total concentration of H 3 O + and OH - ions = 1x H 3 O + = 1x10 -7 OH - = 1x10 -7

20 How pH tells us acidity If the pH of a solution = 1x10 -1 then the amount of H 3 O + =.1 If.1 was money = 10 cents I

21 If the pH of a solution was 1x10 -2 then the H 3 O + concentration =.01 If.01 was money = one penny

22 Which value is MORE acidic – pH1 or pH2 Which is more money a dime or a penny

23 If the concentration of H 3 O + = then the pH = 1x You would need a WHOLE lot of these to just equal ONE PENNY! There are VERY little H 3 O + ions in solution! How many OH - ions will be in this solution?

24 Calculating OH - ions via pH H 3 O + + OH - = 1x If H 3 O + = 1x then 1x OH - = 1x then OH - = 1x x10 -1 (OH - ) =.1 (a dime) 1x (H 3 O + ) = very very very very little So there are MUCH more OH - pH13 solution is a very strong BASE

25 8-2 Reactions with acids and bases Objectives: Write ionic equations for neutralization reactions Identify the products of neutralization reactions Describe the composition of a salt

26 Neutralization Reactions Reactions with Acids and Bases

27 Examples AB + CD  AD + BC The cation of the first compound will form a new bond with the anion of the second compound The cation of the second compound will form a bond with the anion of the first compound

28 HCl + NaOH  HOH + NaCL Notice HOH = H 2 O A strong acid (HCl) reacts with a strong Base (NaOH) to form water and a salt ALWAYS!!!!! Any strong acid any strong base reacts to from water and a salt WATER is NEUTRAL pH =7 Thus “Neutralization” reaction

29 WHAT ARE SPECTATOR IONS Spectator = a bystander of an event Wouldn’t we all love to be a spectator in LONDON this summer for the olympics?

30 Spectator ions are the ions that will eventually form the salt HCl + NaOH  Na + + Cl - + H 2 O H 2 SO 4 + KOH  K + + SO H 2 O In both reactions, once the water evaporates the salts will form NaCl and K 2 SO 4

31 NOT all Neutralization reactions form salts. Weak acid + Strong base  weak base no water still too many OH - ions in solution Strong acid + Weak Base  weak acid no water still too many H 3 O + ions in solution Our body has Natural “buffers” to prevent our blood from being TOO acidic or TOO basic

32 H + aq + HCO - 3aq  H 2 CO 3aq  H 2 O L + CO 2g

33 8-3 Acids, Bases, Salts in the home


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