Acidic Environments

Question 1

If a substance had a pH of 6, would it be acidic, neutral or basic?

Answer 1

Weakly acidic

Question 2

Substance A has a pH of 8. How much more basic is it than substance B, which has a pH of 5?

Answer 2

1,000 times. The pH scale is logarithmic, so pH 6 is 10 times as basic as pH 5, pH 7 is 100 times more so, etc.

Question 3

What does pH stand for?

Answer 3

Parts of hydrogen

Question 4

What is an indicator?

Answer 4

A chemical that change colour as the concentration of hydrogen ions in a solution changes

Question 5

Define the “indicator range”

Answer 5

The range of acidity or basicity over which the colour of an indicator changes colour.

Question 6

Why is pH testing soil important?

Answer 6

Many plants will only grow successfully in soil that is the correct pH for that species. E.g. azaleas will only grow in slightly acidic soil, whilst violets will only grow in slightly basic soil.

Question 7

What two features describe an acidic oxide?

Answer 7

They react with bases to form salts.
They react with water to produce acids.
Not all acidic oxides have both these reactions, but all have at least one.

Question 8

What three features describe a basic oxide?

Answer 8

They react with acids to form salts.
If soluble, they react with water to form alkaline solutions.
They don’t react with alkaline solutions

Question 9

What feature describes an amphoteric oxide?

Answer 9

It will react with both acids AND bases

Question 10

What feature describes a neutral oxide?

Answer 10

It will refuse to react with either acids or bases

Question 11

Are acidic oxides formed primarily by metals or non-metals?

Answer 11

Most acidic oxides are produced by non-metals

Question 12

Are basic oxides formed primarily by metals or non-metals?

Answer 12

Most basic oxides are produced by metals

Question 13

Is carbon dioxide (CO2) an acidic oxide or a basic oxide?

Answer 13

Acidic, because carbon is a non-metal

Question 14

Is diphosphorous pentaoxide (P2O5) an acidic or a basic oxide?

Answer 14

Acidic, because phosphorous is a non-metal

Question 15

Is lithium oxide (Li2O) an acidic or basic oxide?

Answer 15

Basic, because lithium is a metal

Question 16

If an element is on the right-hand side of the periodic table, is it more likely to be an acidic oxide or a basic oxide?

Answer 16

Acidic, because right-hand side elements are non-metals.

Question 17

If an element is on the top of its group in the periodic table, is it more or less acidic than an element at the bottom of the group?

Answer 17

More acidic, because the basicness of an elemental oxide increases down a group.

Question 18

Define Le Chatelier’s principle

Answer 18

“When a change is made to an equilibrium system, the system moves to counteract the imposed change and restore the system to equilibrium.”

Question 19

If a reaction is in dynamic equilibrium, is the reaction continuing?

Answer 19

Yes, however there is no net progress to either the forwards or the backwards reaction.

Question 20

What is the forward reaction in the following equation:

H2 + 0 => H20

Answer 20

H2 + O

Question 21

Are all reactions reversible (and therefore subject to Le Chatelier’s Principle)?

Answer 21

No, many reactions are irreversible

Question 22

What are the three factors that can effect change in a system that is in a state of dynamic equilibrium?

Answer 22

Temperature, concentration and pressure.

Pressure only applies if the system is at least partially gaseous.