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Acids and Bases Unit
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What is an Acid? A solution with an excess of H +1 ions
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How do we know that a chemical is an acid? Most Acids start with an ‘H’ in their chemical formula
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What are the properties of an Acid? Tastes sour Turns blue litmus paper red Reacts strongly with metals Very Corrosive
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Examples of Acids
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What is a Base? A solution with an excess of (OH) -1 ions
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What is another name for a Base? Alkali
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What are the properties of a Base? Tastes bitter Feels slippery Turns red litmus paper blue Corrosive
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Examples of Bases Soap Drano Bleach Chalk
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More Examples of Bases Blood Ammonia
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Stop and Think?!?! Why do you think blood is Basic and not Acidic?
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Warm Up 1. Name three properties of Acids. 2. Name one property that both Acids and Bases have in common.
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So, how do you know if a substance is a Base or an Acid? We use a pH scale
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What does the pH scale measure? This is a measure of the concentration of hydrogen ions
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What is used to indicate the type of substance (Acid or Base) ? Acid-Base Indicators 1. There is blue litmus paper and red litmus paper 2. The Universal indicator 3. Phenolphthalein 4. Cabbage juice
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What happens to litmus paper in the presence of an Acid? Blue litmus paper turns RED in the presence of an acid
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What happens to litmus paper in the presence of a Base? Red litmus paper turns BLUE in the presence of a Base
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On the blank pH scale, label Acids, Bases and Neutral locations!
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Where can Acids be found on the pH scale? pH is less than 7 The lower the number the stronger the acid!!
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Where can Bases be found on the pH scale? pH is more than 7 The higher the number the stronger the base!!
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Where can Neutral substances be found on the pH scale? pH is equal to 7
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Warm Up 1.What element do all acids start with? 2.Where can you find the strongest acids on the pH scale? 3.What color do acids turn litmus paper?
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Let’s go back to Acids!
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What is a Monoprotic acid? There is only ONE hydrogen [H] +1 ion or proton Example: HCl
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What is a Diprotic acid? There are TWO hydrogen [H] +1 ions or protons Example: H 2 SO 4
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What is a Triprotic acid? There are THREE hydrogen [H] +1 ions or protons Ex. H 3 PO 4
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Steps to name acids: Identify the non-metal group first Look at ‘green’ sheet for group name ***If it is not on the ‘green’ sheet it ends in ‘ide’. Drop the non-metal ending and add new acid name
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What are the acid names? No Oxygen w/Oxygen
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Easy way to remember! No “O” use hydro… I ate something icky And ite got nauseous
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HBrHBr H 2 CO 3H 2 CO 3 H 2 SO 3H 2 SO 3 Let’s try together: Examples
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On your own
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So, how do we write the formula for an acid? 1. Identify the cation (for an acid it is always H +1 ) 2. Use the acid name to find the corresponding anion 3. Swap n’ Drop
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Example Hydrochloric acid CationAnionSwap n’ Drop H +1 Cl -1 HCl
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Let’s practice
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Warm Up 05/10/16 For the following, name the acid and identify its type (monoprotic, diprotic or triprotic). Acid FormulaAcid NameType of Acid H 2 Te H 2 CrO 4 HBrO 2
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How do you name bases? 1. Name the metal first, the same name as on the Periodic Table 2. Name the hydroxide (OH) group. 3. If the metal is a transition metal, the charge must be placed in parentheses ( ) in roman numeral (reverse swap n’ drop)
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Example Mg(OH) 2 is magnesium hydroxide
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Example with a Transition Metal Cu(OH) 2 To find the charge we reverse Swap n’ Drop! Cu 1 (OH) 2 Cu +2 (OH) -1 Cu(OH) 2 is copper (II) hydroxide Because the Cu has a +2 charge
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How do you write the formula for bases? Treat the Base Name as a First and Last name. Find the charge for each. Always (OH) -1 for the Last name for a Base. Swap n’ Drop
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Example
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How to calculate pH? You must first know the concentration of hydrogen ions (H +1 )
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How is concentration represented? With empty square brackets, such as [ ].
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So, How to calculate pH? pH= -log[H+]
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Let’s practice 1. Find the pH when the hydrogen ion concentration is 0.0025 M in solution. Ans= 2.60 2. Find the pH when the hydrogen ion concentration is 3.5x10 -5 M in solution. Ans= 4.46
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Other important formulas? Use these to help calculate pH when [H +1 ] is not given: pOH= -log[OH-] pH + pOH=14
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Let’s practice using pOH= -log[OH - ] pH + pOH=14 1. What is the pOH, in a solution that has a hydroxide concentration of 4.82x10 -5 M? Ans= 4.32 Will this solution be Acidic or Basic?
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Do you have an Acidic or Basic solution? Can only be determined by calculating the pH NOT pOH. Be Careful!
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Example 1 continued Will this solution be Acidic or Basic? pH + pOH=14 pH + 4.32=14 pH= 9.68 This solution is Basic!!!
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On your own! 2. What is the pOH, in a solution that has a hydroxide concentration of 2.00x10 -4 M? Will this solution be Basic or Acidic?
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Acids/Bases definitions
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What is an Arrhenius Acid? This type of Acid produces hydrogen ions [H +1 ] in solution.
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What is an Arrhenius Base? This type of Base produces hydroxide ions [OH -1 ] in solution.
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What is the problem with the Arrhenius definition? Not all Bases produces hydroxide ions [OH -1 ] Example: NH 3
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What is a Bronsted-Lowry acid? This type of acid donates hydrogen ions [H +1 ] to another compound.
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What is a Bronsted-Lowry base? This type of base accepts hydrogen ions [H +1 ] from another compound.
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Did Bronsted-Lowry fix the problem? Yes. This definition shows that substances can be bases even though they do not release OH -.
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Example NH 3 is a BASE in water. NH 3 accepts H + to make NH 4 Water is itself an ACID. Water donates H + to make OH -
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What is a conjugate acid-base pair? These are the two compounds involved in the transfer of a hydrogen in a reaction.
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Conjugate Pairs
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How to identify the conjugate pairs? Each pair is made up of the same elements ***The only difference is a hydrogen (H + ).
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Learning Check! Label the acid, base, conjugate acid (CA), and conjugate base (CB) in each reaction: HCl + OH - Cl - + H 2 O H 2 O + H 2 SO 4 HSO 4 - + H 3 O +
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What happens when an Acid and Base react? Neutralization
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What is neutralization? [H + ]=[OH - ] pH=7
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What is produced in a neutralization reaction? Salt and water
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What is a ‘salt’ made up of? It is an ionic compound It contains the metal from the base And the non-metal from the acid.
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