Acids And Bases Flashcards
Arrhenius’ theory
Acids form H³O+ (ionise in water to form H+. Ions can not exist on their own, so they form H³O+)
Bases form OH‐ (dissociate in water to form OH‐)
Lowry-Bronsted’s theory
Acids are proton donors (H+)
Bases are proton acceptors (H+)
Definition of an ampholyte
Any substance that can act as either an acid or base
Definition of a conjugate acid-base pair
Compounds that differ from each other by the presence of H+
(A substance will always be paired with the product it forms)
Describe acids
- sour to the taste
- cause specific colour changes in indicators and plant dyes (litmus = blue to red)
- aqueous acid solutions conduct electricity
- neutralize bases
- have at least 1 H atom that can ionise to form an ion (H+) in an aqueous solution
Describe bases
- alkali = base that is soluble in water
- bitter to taste, soapy to touch (alkali reacts with oils on skin to form soap)
- cause colour changes in indicators and plant dyes (litmus = red to blue)
- alkaline solutions conduct electricity
- neutralize acids
- produce hydroxide ions (OH‐) in aqueous solution
Reaction of acid and metal
Produce a salt and H² gas
Reaction of acid and oxide
Produce a salt and H²O
Reaction of acid and hydroxide
Produce a salt and H²O
Reaction of acid and metal carbonate
Produce a salt, H²O and CO²
Definition of an indicator
A weak organic dye that changes colours at definite pH values
What does a salt contain?
- a cation from the base
- an anion from the acid
How do you find the base in an acid-base reaction?
Combine the cation with O‐², OH‐ , CO³-²
How do you find an acid in an acid-base reaction?
Combine the anion with H+
List 5 examples of indicators
- methyl orange
- methyl red
- bromthymol blue
- neutral red
- phenolphthalein
Formula to determine the pH of an acid
pH = -log [H³O+]
Steps to determine the pH
- Balance reaction of acid with water
- Use molar ratio to determine the concentration of H³O+ molecules
- Plug in and solve
What does Kc mean?
Equilibrium constant
Formula of the equilibrium constant
Kc = [product concentration] ÷ [reactant concentration]
What is the concentration of solids and pure liquids?
One
Equilibrium constant of water
Kw = 1×10‐¹⁴ (at room temperature)
Equilibrium constant of a neutral solution
[H³O+] = [OH‐] = 1×10‐7
Ka value of a strong acid
A strong acid will ionise fully and have a higher concentration of product, therefore, there will be a high Ka value (very little acid left, but a lot of product)
Ka value of weak acids
Weak acids partially ionise and have a lower concentration of product, therefore, they will have a low Ka value (a lot of reactant left, but very little product)
