Unit 5 chemistry

Question 1

How do you convert from oc to K?

Answer 1

Add 273

Question 2

What is enthalpy?

Answer 2

the total heat content of a system

Question 3

what are the standard conditions needed for enthalpy?

Answer 3

pressure of 100kPa, temperature of 298K (250C) and for Reactants and products to be in physical states.

Question 4

What is the symbol for standard conditions?

Answer 4

ɵ

Question 5

What are the units for enthalpy change?

Answer 5

Joules per mole

Question 6

What is meant by system?

Answer 6

a set of things working together as parts of a mechanism

Question 7

What is meant by surroundings?

Answer 7

the things and conditions around a certain item.

Question 8

What is the enthalpy change of formation definition?

Answer 8

When one mole of a substance is formed from its original elements in their standard state under standard conditions

Question 9

What is the enthalpy change of hydration definition?

Answer 9

The energy released when one mole of gaseous ions are dissolved in water under standard conditions

Question 10

What is the enthalpy change of combustion definition?

Answer 10

When one mole of a substance is burned completely in oxygen under standard conditions

Question 11

What is the enthalpy change of reaction definition?

Answer 11

Energy change when reactants form products in molar quantities under standard conditions

Question 12

When the reaction is exothermic, is the energy change positive or negative?

Answer 12

Negative

Question 13

When the reaction is endothermic, is the energy change positive or negative?

Answer 13

Positive

Question 14

What is a hydrocarbon?

Answer 14

A compound made up of just hydrogen and carbon atoms

Question 15

What is the general formula for an alkane?

Answer 15

Cn H2n+2

Question 16

What is the general formula for alkenes?

Answer 16

Cn H2n

Question 17

What are the names of the first 6 alkanes?

Answer 17

Methane, Ethane, Propane, Butane, Pentane, Hexane

Question 18

What are the prefixes for branched alkanes with a chain length of 1 - 4 carbons?

Answer 18

Methyl, Ethyl, Propyl, Butyl

Question 19

What is a structural isomer?

Answer 19

A compound that has the same molecular formula but a different structural formula.

Question 20

What is a cycloalkane?

Answer 20

a hydrocarbon with a molecule containing a ring of carbon atoms joined by single bonds.

Question 21

Why does the boiling and melting point of alkanes increase with chain length?

Answer 21

• As the carbon chain gets longer, there are more electrons in a molecule.
• There are more stronger intermolecular forces between the molecules.
• it takes more energy to break these forces

Question 22

What are the names of the first 6 alkenes?

Answer 22

• Ethene
• Propene
• Butene
• Pentene
• Hexene

Question 23

What is a stereoisomer?

Answer 23

each of two or more compounds differing only in the spatial arrangement of their atoms.

Question 24

What is a symmetrical alkene?

Answer 24

in whose molecule the doubly bonded carbons bear the same ligands.

Question 25

How do you test for an alkene?

Answer 25

A simple test with bromine water

Question 26

What is a saturated hydrocarbon?

Answer 26

that contain only single bonds between carbon atoms.

Question 27

What is a unsaturated hydrocarbon?

Answer 27

that have double or triple covalent bonds between adjacent carbon atoms

Question 28

Describe sigma bonds.

Answer 28

the strongest type of covalent chemical bond. They are formed by head-on overlapping between atomic orbitals.

Question 29

Describe pi bonds.

Answer 29

Covalent chemical bonds where two lobes of an orbital overlap two lobes of an orbital on another atom and this overlap occurs laterally.

Question 30

What is electron pair repulsion theory?

Answer 30

to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms.

Question 31

What are the bond angles for 4 bonding electron pairs, 3 bonding electron pairs and 2 bonding electron pairs?

Answer 31

2- 180 degrees 3- 120 degrees 4- 109.5 degrees

Question 32

Which bond is stronger: sigma or pi bonds?

Answer 32

Sigma bond

Question 33

which bond is stronger: single or double bonds?

Answer 33

Double bond

Question 34

What is the word equation for the combustion reaction (complete)?

Answer 34

Fuel + Oxygen → Carbon dioxide + water

Question 35

What is the word equation for the combustion reaction (incomplete)?

Answer 35

Fuel + Oxygen → Carbon monoxide + water + carbon

Question 36

Why is combustion of fuels important?

Answer 36

The energy that the reaction produces can be used to heat water, cook food, generate electricity or even power vehicles.

Question 37

What are the conditions for halogenation?

Answer 37

Uv light and heat

Question 38

What is homolytic fission.

Answer 38

chemical bond dissociation of a molecular bond by a process where each of the fragments gains one of the originally bonded electrons.

Question 39

What is a free radical?

Answer 39

an uncharged molecule (typically highly reactive and short-lived) having an unpaired electron.

Question 40

What are the three steps of a free radical substitution reaction and state what happens in each step.

Answer 40

- Initiation- creates a radical species. - Propagation- Once a reactive free radical is generated, it can form new free radicals. - Termination- two free radical species react with each other to form a stable, non-radical adduct.

Question 41

What factors affect the standard enthalpy change of hydration?

Answer 41

- Charge on the ion | - Size of the ion

Question 42

What is the equation for calculating the standard enthalpy of a reaction?

Answer 42

Sum of standard enthalpy of products- Sum of standard enthalpy of reactants

Question 43

What is the equation for calculating the standard enthalpy of a formation?

Answer 43

Sum of standard enthalpy of elements- Sum of standard enthalpy of compound

Question 44

What are the 5 stages of the bayer process?

Answer 44

- Crush the Bauxite - Removal of any impurities - filter out solid impurities - Allow it to crystalise to Al (OH)3 - Heat it in a rotary kiln to form Alumia

Question 45

What are the 2 stages of the Kroll process?

Answer 45

1- Titanium oxide, coke and chlorine are heated together at 900 degrees to form titanium chloride 2- Magnesium is used as a reducing agent to form titanium

Question 46

What are the raw materials for the contact process?

Answer 46

Sulfur + air + water

Question 47

In a diaphragm cell, what metal is the anode made out of?

Answer 47

Titanium

Question 48

In a diaphragm cell, what metal is the cathode made out of?

Answer 48

Steel

Question 49

In a diaphragm cell, what is produced at the cathode

Answer 49

brine containing sodium hydroxide + hydrogen gas

Question 50

In a diaphragm cell, what is produced at the anode

Answer 50

Chlorine gas

Question 51

In a membrane cell,what metal is the anode made out of?

Answer 51

titanium

Question 52

In a membrane cell,what metal is the cathode made out of?

Answer 52

nickel