Acids and bases, stoichiometry and moles test

Question 1

What does it mean when we say this chemical is classed as an acid?

Answer 1

Acids are compounds or ions that donate protons, whereas bases are compounds or ions that accept protons.

Question 2

What is a hydronium ion?

Answer 2

Hydronoium is a cation, formed by water plus an extra hydrogen. H30

Question 3

Monoprotic, vs diprotic vs triprotic.

Answer 3

Monoprotic acids can only release one proton or hydrogen ion per molecule. Diprotic can release up to 2, triprotic can release up to 3.

Question 4

What is ionisation?

Answer 4

Ionisation is the process by which an atom or molecule gains or loses electrons, resulting in the formation of an ion.

Question 5

What is the difference between a strong acid and a weak acid?

Answer 5

Strong acids ionise completely - 100% ionisation. Weak acids ionise partially - less than 10% ionisation.

Question 6

What do acids do in water?

Answer 6

Ionise

Question 7

What happens to electrical current if an acid is added to water.

Answer 7

Increases electrical current due to the transfer and movement of the H+ ions.

Question 8

Examples of strong acids:

Answer 8

Sulfuric Acid, hydrochloric acid and nitric acid.

Question 9

What is the arrow for complete ionisation.

Answer 9

Single arrow

Question 10

What is the arrows for partial ionisation.

Answer 10

Two arrows same length.

Question 11

What is the arrows for minimal ionisation.

Answer 11

Two arrows, one shorter than the other.

Question 12

pH value of strong acids vs weak acids.

Answer 12

Strong acids ph roughly 1, whereas weak acids pH 2-6.

Question 13

What will happen when a strong acid is mixed with a weak base?

Answer 13

The strong acid will almost completely ionise in water and disassociate the hydrogen ions. However because it is a weak base not all of those will be accepted by the base. There will be leftover H+ ions. The reaction will not fully neutralise.

Question 14

Two solutions, one of hydrochloric acid and one of acetic acid, both have a pH of 4.
Explain how can this be correct, even though one is a weak acid and one is a strong acid?

Answer 14

HCl is a strong acid completely ionises, very little acetic acid ionises in water. Therefore to achieve the same pH a much higher concentration of acetic acid is required. And a lower concentration of HCl to compensate for the differences in ionisation.

Question 15

What is nitric acid?

Answer 15

HNO3

Question 16

What is acetic acid?

Answer 16

CH3COOH

Question 17

What is bicarbonate?

Answer 17

Hydrogen carbonate. HCO3

Question 18

What is carbonic acid?

Answer 18

H2CO3 - can convert to water and carbon dioxide.

Question 19

What is an amphiprotic substance?

Answer 19

An amphiprotic substance is a proton-bearing molecule that is capable of donating its proton as well as accepting an additional proton.

Question 20

Equation for why rainwater is slightly acidic?

Answer 20

H20 + CO2 - H2CO3 (Carbonic acid)

Question 21

Why would you swirl the acid during a titration?

Answer 21

To evenly distribute the acid/alkali.

Question 22

What colour is phenolphalein in acidic solutions?

Answer 22

Colourless, it is pink in alkaline solutions.

Question 23

What is the natural pH of rainwater? Why?

Answer 23

The presence of this carbonic acid means that the pH of rainwater is naturally around pH 5.6.

Question 24

What is the definition of acid rain?

Answer 24

Acid rain is defined as rainwater that has a pH less than 5.6. The production of acid rain occurs when acids (stronger than carbonic) form as a result of sulphur and nitrogen in the atmosphere.

Question 25

Name two oxides that are produced in the combustion of fossil fuels

Answer 25

SO2 + N02 (sulfur dioxide and nitrogen dioxide)

Question 26

What are some damaging effects of acid rain?

Answer 26

Damage to plants, acidification of ocean and water ways, damage to fish gills. damage to buildings, particularly limestone and marble.

Question 27

Definition of molar mass

Answer 27

is the mass in grams of 1 mole of a substance

Question 28

In a galvanic cell, how do you tell which half cell is the anode, and which is the cathode?

Answer 28

The more reactive of the 2 metals is the anode, the negative electrode. The less rective of the 2 metals is called the cathode, the positive electrode.

Question 29

In the galvanic cell, which half cells do oxidation and reduction take place.

Answer 29

Oxidation always takes place at the anode, reduction at the cathode.

Question 30

What is the purpose of the salt bridge in a galvanic cell?

Answer 30

The purpose of the salt bridge is to keep the solutions electrically neutral and allow the free flow of ions from one cell to another. Without the salt bridge, positive and negative charges will build up around the electrodes causing the reaction to stop.

Question 31

What are the indicators of an oxidation reaction?

Answer 31

Loosing electrons, gaining oxygen. Loosing hydrogen. Increase in oxidation number. It is called an oxidation number, therefore an increase.

Question 32

What are the indicators of a reduction reaction?

Answer 32

Gaining electrons, loosing oxygen. Gaining hydrogen. Decrease in oxygdation numbers, because of the gained electrons.

Question 33

What is an oxidant?

Answer 33

The one that is being reduced. An oxidant causes another substance to be oxidised.

Question 34

What is a reductant?

Answer 34

A reductant is the one being oxidised. It causes another substance to be reduced.

Question 35

Define a galvanic cell? What are it’s components and how does the system work?

Answer 35

A galvanic cell is a system that.
-consists of electrodes (metal or carbon rods)
That dip into an electrolyte
In which a chemical reaction happens
-That generates an electrical current.

Question 36

Which directions do the electrons travel along the wire in a galvanic cell?

Answer 36

From the anode to the cathode.