Acids and Bases Day 2 A beaker of
Acids and Bases Day 2
A beaker of aqueous solution has a p. H of 7. 2 and the desired p. H is 9. 4. Should an acid or base be added?
A beaker of aqueous solution has a p. H of 7. 2 and the desired p. H is 9. 4. Should an acid or base be added? Base, because to increase the p. H, the H+ needs to be at a lower concentration. Bases will either increase the OH- levels or directly accept the Hydrogen ions
Arrhenius Acids and Bases ● Producers – Acids produce H+ – Bases produce OH- ● Acids increase H 3 O+ concentration ● Bases increase OH- concentration
Brønsted-Lowry ● Hydrogen Donor or Hydrogen acceptor – Acids donate Hydrogen Ions – Bases accept Hydrogen Ions
Brønsted-Lowry cont. ● ● ● Conjugate Acids and Base When a base accepts a Hydrogen Ion/Proton from an acid, it becomes a conjugate base When an acid donates a Hydrogen Ion/Proton to a base, it becomes a conjugate acid
Dissociation/Ionization ● ● ● Acids and Bases break off their ions ● Acid example: HCl + H 2 O H 3 O+ + Cl- ● Base example: Na. OH Na+ + OH- Acids will only dissociate in a solution Bases can dissociate without another reactant, but it is rare
General formulas ● p. H + p. OH = 14 ● 14 – p. H = p. OH ● ● ● 14 – p. OH = p. H OH- = 10^(-p. OH) ● p. OH = -log(OH ) H+ = 10^(-p. H) + ● p. H = -log(H )
Ka and p. Ka ● ● ● The strength of an acid or base is determined by how easily it dissociates/ionizes ● The easier it is for the substance to dissociate the stronger it is Ka = [H 3 O+][A-] / [HA] p. Ka = -log 10(Ka) Calculations with these concepts will be minimal Higher p. Ka means more basic Lower p. Ka (even going into the negatives) means more acidity
Concentration/dilution vs strength ● ● ● Concentration is density and NOT strength ● You determine concentration by how much of an acid or base is in the solution Strength is determined by how easily ionized a substance is A strong acid that is diluted can have a higher p. H (less acidic) than a weak acid that is concentrated
Molarity (M) ● Measures concentration levels ● Applies for both Acids and Bases ● Moles / Liters ● c = n/V
Which of the following substances is an Arrhenius Base? • A) Cs. OH • B) H 2 SO 4 • C) HI • D) HCl. O 4
All Arrhenius Bases have “OH” in the molecular formula. This is because they are defined by increasing the OHconcentration • A) Cs. OH
Which of the following substances is an Arrhenius Base? • A) HBr • B) Na. Cl. O • C) HSO 3 • D) KOH
All Arrhenius Bases have “OH” in the molecular formula. This is because they are defined by increasing the OH- concentration. Additionally, B) Na. Cl. O- is incorrect because it does not have a hydroxide (OH) although it is a strong base with a powerful negative charge. • D) KOH is the answer.
How would HNO 3 dissociate in water?
How would HNO 3 dissociate in water? First, note that the Hydrogen is written on the left side of the formula. This likely indicates that the substance is an acid. Next, use your reference sheet and memory to confirm that NO 3 is a polyatomic ion. This means that it will likely break off during ionization and leaving the Hydrogen alone. Thus, the substance is an acid and will dissociate in the following manner: HNO 3 + H 2 O �H 3 O+ + NO 3 -
● Write and balance the reaction for the following acid-base reactions AND label the acid, base, and salt in each: HNO 2 + Ca(OH) 2 �
HNO 2 + Ca(OH) 2 � ● ● ● First, understand which is the acid and base. Acids normally have the Hydrogens on the left/front. Bases have their hydrogens on the right/back or don’t have them at all. HNO 2 (Acid) + Ca(OH)2 (Base) � The Hydrogen and Hydroxide will combine to make water and the Ca and NO 2 will combine to make the salt ● Ca(NO 2)2 (Salt) + H 2 O ● HNO 2 (Acid) + Ca(OH)2 (Base) � Ca(NO 2)2 (Salt) + H 2 O ● Then it needs to be balanced. ● 2 HNO 2 (Acid) + Ca(OH)2 (Base) � Ca(NO 2)2 (Salt) + 2 H 2 O
What is the H+ concentration if the p. H is 4. 2? ● A) 1. 66 E-4 ● B) 6. 31 E-5 ● C) 1. 58 E 4 ● D) 3. 16 E 5
Recall the general formulas. If the p. H is given, finding the H+ concentration requires you use: H+=10^(-p. H) H+=10^(-4. 2) = ● B) 6. 31 E-5
What is the p. H if the OHconcentration is 3. 16 E-9? ● A) 8. 5 p. H ● B) 7. 5 p. H ● C) 6. 5 p. H ● D) 5. 5 p. H
First, take the OH- concentration and find the p. OH=-log(OH-) p. OH=-log(3. 16 E-9) p. OH=8. 5 Then, the p. H can be found because the general formulas state that 14=p. H+p. OH 14 -p. OH=p. H 14 -8. 5=5. 5 ● D) 5. 5 p. H
What is the p. OH if the p concentration is 6. 3 E-6? ● A) 5. 2 p. H ● B) 4. 2 p. H ● C) 9. 8 p. H ● D) 8. 8 p. H
First, take the H+ concentration and find the p. H=-log(H+) p. H=-log(6. 3 E-6) p. H=5. 2 Then, the p. OH can be found because the general formulas state that 14=p. H+p. OH 14 -p. H=p. OH 14 -5. 2=8. 8 ● D) 8. 8 p. OH
What is the molarity if 5 moles of HCl is placed in 100 Liters of water? ● A) 5 M ● B) 0. 5 M ● C) 0. 05 M ● D) 0. 005 M
n/V = c moles divided by volume equals concentration 5 mol / 100 L = 0. 05 M ● C) 0. 05 M
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