CHE

Question 1

Define reagent

Answer 1

A reactant which is added to cause a specific chemical reaction

Question 2

What products does combustion reaction produce?

Answer 2

CO2 and H2O

Question 3

What produces does incomplete combustion produce

Answer 3

CO, H2O, C (soot)

Question 4

Define global warming

Answer 4

The long term heating of the Earth’s surface due to greenhouse gas emissions trapping the sun’s heat.

Question 5

Define greenhouse gases and give three example

Answer 5

Gases which absorb infrared radiation, thereby contributing to the greenhouse effect. e.g. carbon dioxide, carbon monoxide and methane.

Question 6

Define specific heat capacity

Answer 6

The heat energy required to raise the temperature of 1 gram (of water)
by 1 degree celsius.

Question 7

Reagent for alkene to alcohol

Answer 7

H2O / H+

Question 8

Reagent for alcohol to alkene

Answer 8

conc. H2SO4

Question 9

Reagent for alkene to alkane

Answer 9

H2 / Pt

Question 10

Reagent for alkene to haloalkane

Answer 10

X2 or HX

Question 11

Reagent for alcohol to haloalkane

Answer 11

SOCl2 or PCI5

Question 12

Reagent for haloalkane to alkene

Answer 12

KOH(alc)

Question 13

Reagent for haloalkane to alcohol

Answer 13

KOH(aq)

Question 14

Reagent for alkane to haloalkane

Answer 14

X2 / UV light

Question 15

Define specific energy

Answer 15

energy per unit mass

Question 16

How do you calculate the amount of particles in an object?

Answer 16

Number of particles = moles x avogadro’s number

Question 17

Define concentration

Answer 17

measure of how much dissolved substance there is in a given solvent

Question 18

How do we convert molL-1 to gmol-1?

Answer 18

multiplying by molar mass

Question 19

Define titration

Answer 19

a practical technique that is used to find the concentration of an unknown solution

Question 20

Explain the steps to carry out a titration (figuring out the concentration of an unknown solution)

Answer 20

Start with two solutions:
One has a known concentration (called the “standard solution”).
The other has an unknown concentration (what you’re trying to find).

Measure a specific amount of the unknown solution into a flask (using a tool called a pipette).

Fill a burette (a tube with a tap) with the known solution.

Slowly drip the known solution from the burette into the flask.

Add an indicator (a chemical that changes color) to show when the reaction is complete.

Record how much of the known solution (called the “titre”) you added to fully react with the unknown solution.

Use this volume, along with the known solution’s concentration, to calculate the concentration of the unknown solution.

Question 21

Define dilution factor

Answer 21

An amount you want to dilute your concentrated acid solution by

Question 22

What are some common controlled variables for titrations?

Answer 22

• chemical exposure to air/heat/UV light
• amount of indicator added to each trial
• same initial concentration of chemicals

Question 23

What is a titre?

Answer 23

How much of the known solution is added to fully react with the unknown solution.

Question 24

How does water contribute to global warming?

Answer 24

Water vapor is a natural greenhouse gas that traps heat in the atmosphere.

As the planet gets warmer, more water evaporates, adding even more heat and creating a cycle that makes warming worse.

Question 25

How does methane contribute to global warming?

Answer 25

Methane is a very strong greenhouse gas that traps a lot of heat. (not for a long time) It comes from farming, landfills, and fossil fuels, and it eventually turns into CO₂ and water, which also cause warming.

Question 26

How does carbon dioxide contribute to global warming?

Answer 26

Carbon dioxide is the main gas causing global warming because we produce so much of it by burning fossil fuels. It traps heat in the atmosphere and stays there for a very long time.

Question 27

How does carbon monoxide contribute to global warming?

Answer 27

Carbon monoxide doesn’t trap heat directly, but it makes global warming worse by helping methane stay in the air longer, which increases warming. It comes from things like burning fuel incompletely.

Question 28

State the properties of short-chain hydrocarbons when they undergo combustion

Answer 28

Burn more completely, producing mainly CO₂ and H₂O. (CO2 contributes to global warming) Produce a blue flame, indicating clean combustion with minimal soot. High specific energy, produce more energy for the same amount of fuel.

Question 29

State the properties of long-chain hydrocarbons when they undergo combustion

Answer 29

Tend to burn less completely, especially under limited oxygen, producing soot (C), carbon monoxide (CO) Produce a yellow, smoky flame due to incomplete combustion. Low specific energy, produce less energy for the same amount of fuel

Question 30

Why is CO harmful to humans + the environment

Answer 30

Carbon monoxide (CO) is harmful because it replaces oxygen in the blood, causing health problems like dizziness and suffocation. It also contributes to air pollution, which harms the environment and human health.

Question 31

Why is methane harmful to humans?

Answer 31

Not directly harmful to human health, but can contribute in irritating the lungs

Question 32

Why is carbon dioxide harmful to humans?

Answer 32

High concentrations can cause suffocation in enclosed spaces (not harmful outdoors)

Question 33

Why is carbon monoxide harmful to humans?

Answer 33

Inhalation of fine particulate matter can lead to respiratory and cardiovascular diseases

Question 34

Why is water vapour harmful to humans?

Answer 34

Generally not harmful, but high humidity can worsen breathing problems for people with respiratory conditions.

Question 35

How do you calculate estimated dilution factor?

Answer 35

mini titration titre x pipette volume / ideal titre volume

Question 36

How to calculate available dilution factor?

Answer 36

volume of volumetric flask / volume of pipette

Question 37

How to calculate expected titre?

Answer 37

Mini titration titre x pipette volume for titration / dilution factor

Question 38

Define mole

Answer 38

the number of particles in a substance

Question 39

Why is there a minimum of 3 titrations carried out?

Answer 39

Ensures the accuracy and consistency of results and confirm that they are not a random occurrence.

Question 40

Why do we dilute?

Answer 40

Consumer products are often too concentrated. This leads to a titre volume that is way too big.

Question 41

What is the ideal titre volume?

Answer 41

10-25mL

Question 42

Why do we need a titre range more than 10mL?

Answer 42

When the titre range falls below 10 mL, the error in measuring the volume becomes too large, reducing precision.

Question 43

Why do we need a titre range less than 25mL?

Answer 43

When above 20mL, you waste more titrant, which is not ideal for cost-efficiency or minimizing the number of refills needed. The fewer times you refill the burette, the less opportunity there is for inaccuracies

Question 44

What is an analyte

Answer 44

the solution being analysed (one that we find the concentration for)