Unit 4 test

Question 1

What are some characteristics of a solution

Answer 1

homogenous mixture
transparent (clear)
may be coloured
Dissolved particles are very small ∴ can not be filtered

Question 2

Solute

Answer 2

Solute – the substance that is being dissolved in a solvent
e.g. sugar

Question 3

Solvent

Answer 3

Solvent – the medium in which a solute is dissolved (often a liquid) e.g. water

Question 4

What does soluble mean

Answer 4

When a solid dissolves in a liquid solvent we say that it is SOLUBLE in that solvent

Question 5

What does insoluable mean

Answer 5

If the solute does not substantially dissolve in a given liquid we say that it is INSOLUBLE

Question 6

What is Miscible

Answer 6

When two liquids dissolve in each other they are said to be MISCIBLE (usually the liquid present in the smaller quantity is regarded as the solute)

Question 7

What is immiscible

Answer 7

IMMISCIBLE liquids will not dissolve in each other

Question 8

What are electrolytes

Answer 8

Electrolytes – solutions that conduct electricity because they contain ions

Question 9

Why does like dissolve like

Answer 9

Non polar molecules are held together by weak London forces

But – one weakly held non-polar substance could go “between” another weakly held non-polar substance

Polar compounds surround polar ions

Question 10

What is a saturated solution

Answer 10

One in which no more of a particular solute is able to dissolve. (It’s full!)

Question 11

Unsaturated solution

Answer 11

One that is not saturated.

Question 12

Supersaturated solution

Answer 12

contains more solute than should dissolve in the solution

Question 13

Concentration

Answer 13

The amount of solute per quantity of solvent

Question 14

m/v

Answer 14

Chemists often express the concentration of an unsaturated solution as the mass of solute dissolved per volume of the solution.
This is different from solubility.
It is usually expressed as a percent relationship.
A mass/volume percent gives the mass of solute dissolved in a volume of solution, expressed as a percent.
The mass/volume percent is also referred to as the percent (m/v).

Can be over 100%

Question 15

m/m or w/w

Answer 15

The percent of sodium fluoride in the toothpaste is usually given as a w/w percent.
The concentration of a solid solution, such as an alloy, is usually expressed as a mass/mass percent.
A mass/mass percent gives the mass of a solute divided by the mass of solution, expressed as a percent.
The mass/mass percent is also referred to as the percent (m/m), or the mass percent.
It is often inaccurately referred to as a weight (w/w) percent, as well.

Question 16

v/v

Answer 16

You can see this type of concentration on a bottle of rubbing alcohol from a drugstore.
When mixing two liquids to form a solution, it is easier to measure their volumes than their masses.
A volume/volume percent gives the volume of solute divided by the volume of solution, expressed as a percent.
The volume/volume percent is also referred to as the volume percent concentration, volume percent, percent (v/v), or the percent by volume.

Question 17

Concentration in Parts per Million and Parts per Billion

Answer 17

The concentration of a very small quantity of a substance in the human body, or in the environment, can be expressed in parts per million (ppm) and parts per billion (ppb).

Both parts per million and parts per billion are usually mass/mass relationships. They describe the amount of solute that is present in a solution.

For example, scientists can measure the pollutants and other trace contaminants in water, air and soil by looking at small samples.

Very low concentration is expressed in:
ppm – parts per million
ppb – parts per billion
ppt – parts per trillion

Question 18

Molar Concentration

Answer 18

most useful unit of concentration
Num of moles of solute in 1L of solution
AKA Molarity (M)

Question 19

What is a solubility graph

Answer 19

A graph created by heating a certain mass of solute in 100 mL of water then cooling until precipitation begins.

Question 20

Conjugate acid

Answer 20

A “conjugate acid” is the result of having received an extra Hydrogen Ion (Proton)

EG:

NH3(g) (base) + H2O(l) (acid) ——> NH4+(aq) (Conjugate Acid) + OH-(aq) (Conjugate base)

Question 21

Conjugate base

Answer 21

A “conjugate base” is the result of having lost a Hydrogen Ion (Proton)

EG:

NH3(g) + H2O(l) ——> NH4+(aq) + OH-(aq)
Base Acid ——> Conjugate Acid Conjugate Base

Question 22

Common strong bases

Answer 22

Sodium hydroxide (NaOH)
Potassium hydroxide (KOH)
Calcium hydroxide (Ca(OH)2)
Strontium hydroxide (Sr(OH)2)
Barium hydroxide (Ba(OH)2)

Question 23

What is a strong acid

Answer 23

When an acid dissolves in water, a proton (hydrogen ion) is transferred to a water molecule to produce a hydronium ion and a negative ion depending on what acid you are starting from.

In the general case ..
HA +H2O ↔ H3O+ + A-

These reactions are all reversible, but in some cases, the acid is so good at giving away hydrogen ions that we can think of the reaction as being one-way. The acid is virtually 100% ionised.
For example, when hydrogen chloride dissolves in water to make hydrochloric acid, so little of the reverse reaction happens that we can write:
H2O(l) + HCl(g) → H3O+(aq) + Cl-(aq)
At any one time, virtually 100% of the hydrogen chloride will have reacted to produce hydroxonium ions and chloride ions. Hydrogen chloride is described as a strong acid.
A strong acid is one which is virtually 100% ionised in solution.
Other common strong acids include sulphuric acid and nitric acid.

Question 24

What is an acid

Answer 24

An acid is anything from which a proton (H+ ion) can be removed

Question 25

What is a base

Answer 25

A base is anything that can remove a proton from an acid.