Name:
____/____/_________
WS04 – Electrical Conductivity, Acids, Bases, Salts
I.
GRADE 10
Electrical Conductivity
Ability to allow an electric current to flow through it.
• Electrolyte: substance in which an electric current flow through the solution.
• Nonelectrolytes: substances soluble in water, but do not conduct electricity.
• Electrolyte solution: substance that contain an electrolyte
Example 1 – Classify the substances below in electrolytes or nonelectrolytes:
NaCl dissolved in water
C12H22O11 dissolved in water
HCl dissolved in water
Example 2 – Complete:
When an electrolyte is dissolved, __________ are formed, conducing electricity.
When an nonelectrolyte is dissolved, ____________ are formed, _____ conducing electricity.
II.
Electrolytic Dissociation
Separation of a dissolved compound into two ions of opposite charges.
Example 2 – Complete the chemical equation of the electrolytic dissociation below:
a. Dissociation of NaCl:
b. Dissociation of C12H22O11:
c. Dissociation of HCl:
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Name:
____/____/_________
WS04 – Electrical Conductivity, Acids, Bases, Salts
III.
GRADE 10
The Strength of Electrolytes
Degree to which it dissociates into ions. The higher the degree of dissociation, the
stronger the electrolyte.
• Strong electrolyte: Practically all the molecules of the solute dissociate in water,
forming ions.
• Weak electrolyte: Only some of the molecules dissociate, forming ions. The
others remains neutral (neither positively or negatively charged)
• Nonelectrolyte: None of the molecules dissociate, forming ions.
Example 3 – Observe the degree of dissociation of the substances below and classify in
strong, weak or nonelectrolyte:
a)
Initial Condition
→
NaCl(s)
Na+(aq) +
100 molecules
After dissolution
b)
100 ions
HF(aq)
→
Initial Condition
100 molecules
After dissolution
92 molecules
c)
C12H22O11(s)
Initial Condition
100 molecules
After dissolution
Cl-(aq)
100 ions
H+(aq) +
8 ions
→
F-(aq)
8 ions
C12H22O11(aq)
100 molecules
2
Name:
____/____/_________
WS04 – Electrical Conductivity, Acids, Bases, Salts
IV.
GRADE 10
Types of Electrolytes
Acids, bases and salts are three important types of electrolytes with different
properties.
• Acids:
i. Sour taste
ii. Releases H+ (cation) ions in an aqueous solution
iii. Chemical formula often begins with the symbol of a hydrogen atom (H).
Exception – Acetic acid (vinegar) – CH3COOH
iv. Name: substance + ic + acid
v. Litmus paper – turns red
• Bases:
i. Bitter taste
ii. Releases OH- (anion) ions in an aqueous solution
iii. Chemical formula often begins with a metal and usually ends with the group
OH. Exception – ammonium hydroxide (NH4OH)
iv. Name: substance + hydroxide
v. Litmus paper – turns blue
• Salts:
i. Salty taste
ii. Releases a cation and an anion other than H+ and OHiii. Chemical formula formed by a metal and one or more non-metals
iv. Name: metal + nonmetal + ide (or ate, ite)
v. Litmus paper – no reaction (no change color)
3
Name:
____/____/_________
WS04 – Electrical Conductivity, Acids, Bases, Salts
GRADE 10
Example 4 – Write the chemical formula, the dissociation and classify in acids, bases or salts:
Substance
Chemical formula
Dissociation
Classification
Hydrochloric acid
Sodium hydroxide
Sodium chloride
Sulphuric acid
Silver nitrate
Magnesium hydroxide
Calcium chloride
Acetic acid
Ammonium hydroxide
V.
pH (potential Hydrogen)
The pH scale (ranges from 0 to 14) is a scale used to rank the relative basicity or
acidity of substances based on the amount of hydrogen ion (H+) activity in a substance.
• pH < 7: acidic
• pH = 7: neutral
• pH > 7: basic
The pH scale is logarithmic, which means that a difference of one unit between
two substances indicates that one of the substances is 10 times more acidic or more
basic than the other.
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Name:
____/____/_________
WS04 – Electrical Conductivity, Acids, Bases, Salts
GRADE 10
Example 5 – Complete the table with the pH of common substances and classify in acidic,
basic or neutral.
Substance
pH
Classification
Bleach
Gastric Acid
Soda
Pure water
Ammonia
Saliva
Battery acid
Drain cleaner
Urine
Example 6 – Observing the table above, calculate how many times one substance is more
acidic (or basic) than the other substance.
a) Bleach and drain cleaner
b) Gastric acid and soda
c) Acid rain and pure water
5
Name:
____/____/_________
WS04 – Electrical Conductivity, Acids, Bases, Salts
GRADE 10
PRACTICE
1. Name and classify the substances in acids, bases, or salts and write the balance
chemical equation to represent the dissociation:
Name
Chemical formula
Dissociation
Classification
KCl
HF
HCl
KOH
FeBr3
NaNO3
HNO3
NaCl
CaCl2
NH4Cl
NaOH
Na2SO4
Mg(OH)2
H3PO4
CuCl2
H2SO4
Ca(OH)2
H2CO3
NH4OH
Al(NO2)3
HNO2
H2 S
HBr
6
Name:
____/____/_________
WS04 – Electrical Conductivity, Acids, Bases, Salts
GRADE 10
2. Write balanced chemical equations to represent the dissociation of the compounds below
and classify them in acid, base or salt:
a. Sodium acetate
b. Ammonium sulfate
c. Calcium carbonate
d. Potassium carbonate
e. Sodium hydroxide
f. Iron (II) sulfate
g. Lead (II) phosphate
h. Iron (III) chloride
i. Copper (II) sulfate
j. Mercury (II) sulfide
k. Zinc chloride
l. Lead (II) acetate
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Name:
____/____/_________
WS04 – Electrical Conductivity, Acids, Bases, Salts
GRADE 10
3. A student mixes strawberry and water. A pH meter shows a pH of 5.4.
a. Is strawberry acidic, basic, or neutral?
b. In this mixture, must there be more of hydrogen ions or hydroxide ions? Why?
4. A student adds alka-seltzer tablet to the strawberry mixture and stirs. The pH meter now
reads 8.3. What was released by the alka-seltzer tablet to cause this change?
5. Bromothymol blue is a chemical indicator that is blue in basic and neutral solutions, an
turns greenish and then yellow as the solution becomes more and more acidic. Fill the
table below with the color would bromothymol blue would be and answer the following
questions:
Situation
pH
Water directly out of tap
pH = 7.2
Bromothymol blue color
pH after exhaled air is blown through a straw into pH = 5.1
water for 5 min
pH with 2mL of bleach added to the water
pH = 9.4
pH with instant coffee added to the water
pH = 5.0
pH after an aquatic plant is grown in water for pH = 7.7
three days in bright sunlight
pH after a snail has lived in water for three days
pH = 5.8
a. What effect does carbon dioxide have on tap water?
b. Is bleach an acid or a base?
c. Is coffee an acid or a base?
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