VCE Chemistry Acids & Bases Concentration v Strength

VCE CHEMISTRY

Acids & BasesStrength v Concentration

Objective:To distinguish between strength & concentration of acids & bases

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1. What is an acid & a base ?2. Name 3 Acids & 3 Bases3. Can you write ionisation of:

Sulphuric Acid Sodium Hydroxide

Discuss for 1 Minute in PairsNo referring to Notes or Computers

Brønsted-Lowry Theory: 

Acids are proton donors (Think AD)Bases are proton acceptors

Arrhenius Theory: 

Acids generate H+ ionsBases generate OH- ions.

Sulfuric Acid

H2SO4 2H+ + SO4 Sodium Hydroxide

NaOH Na+ + OH-

2-

Reversible – remember constantlydissociate & reassociate

Strength Concentration

Acids & Bases are measured by:

 Strength

Base Basic Solution

Acid Acidic Solution

In water an acid or base molecule can break

apart DISSOCIATIONAcids form the hydronium ion(H3O+ also see H+)

Dissociation in solution

Strength

The degree of dissociation defines strong or weak acid.Which is Strong or Weak acid ?

-

Strength

Strong acid

Weak acid  H O

HOF

H H

H

H H F F+ + +

Weak acid

Water hydronium ion

-+

ions

Strength

Strong acid or base completely dissociates in solution

Weak acid or base only partially dissociates in solution. 

H OH

OFH H

H

H H F F+ + +

Weak acid

Water hydronium ion

-+

ions

Strong or Weak ?

Strong or Weak ?

 Concentration

Number of moles per volume within solution

Amount of acid or base in solution

Less Concentrated

means less Na+ OH_ but

still strong base

Less Concentrated means less H3O+ Cl- but still strong acid

In pairs, draw a beaker & show with ions;

Highly Concentrated Weak Acid (HF)Weakly concentrated Weak Acid Weakly Concentrated Strong Acid (HCl)Highly concentrated Strong Acid

Review

Strength - Dissociation in solnStrong acid completely dissociatesWeak acid partially dissociates

Concentration - Amount in solnWeak low amountHigh high amount

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