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Question 1

why do elements/compounds in a mixture retain their individual properties?

Answer 1

they are not chemically bonded together

Question 2

explain the difference between a homogeneous and a heterogeneous mixture

Answer 2

Heterogeneous mixtures have visually distinguishable components, while homogeneous mixtures appear uniform throughout.

Question 3

define a mole

Answer 3

a fixed number of particles referring to the amount, n, of substance

Question 4

units for molar mass

Answer 4

g/mol

Question 5

define molar mass

Answer 5

the ratio between the mass and the amount of substance (measured in moles)

Question 6

difference between empirical and molecular formulae of compounds

Answer 6

simplest ratio vs actual number of atoms present in a molecule

Question 7

what are standard temperature and pressure?

Answer 7

0 degrees celsius (273K) and 100kPa

Question 8

what is true at standard temperature and pressure?

Answer 8

the molar volume of an ideal gas is 22.7 dm3/mol

Question 9

give the equation for molar volume, as well as its usual value

Answer 9

volume (dm3)/ moles. 22.7

Question 10

give the equation for the molar volume of an ideal gas and its usual value

Answer 10

22.7= vol/mol

Question 11

what does 1 mol of gas contain?

Answer 11

6.02x10^23 atoms or molecules of the gas

Question 12

state Avogadro’s law

Answer 12

equal volumes of any gas measured at the same temperature and pressure contain the same number of molecules

Question 13

law for volume vs pressure

Answer 13

p=1/v
p1v1=p2v2

Question 14

law for volume vs temperature

Answer 14

v is proportional to t (in K)
v1/t1=v2/t2

Question 15

law for pressure vs temperature

Answer 15

p is proportional to t
p1/t1=p2/t2

Question 16

combined gas law

Answer 16

p1v1/t1= p2v2/t2

Question 17

ideal gas equation and units

Answer 17

pV=nRT
Pa for pressure
m3 for volume
K for temperature
R is the gas constant

Question 18

describe the assumptions behind the kinetic theory of gases (5)

Answer 18

• The gas molecules are moving very fast and randomly
• The molecules hardly have any volume
• The gas molecules do not attract or repel each other (no intermolecular forces)
• No kinetic energy is lost when the gas molecules collide with each other (elastic collisions)
• The temperature of the gas is directly proportional to the average kinetic energy of the molecules

Question 19

gases that follow the kinetic theory of gases are called

Answer 19

ideal gases

Question 20

why do gases deviate from ideal behaviour at higher temperatures and pressures?

Answer 20

Assumptions about volume:
The kinetic theory assumes that the volume the actual gas molecules themselves take up is tiny compared to the volume the gas occupies in a container and can be ignored
This is broadly true for gases at normal conditions, but becomes increasingly inaccurate at low temperatures and high pressures
At these conditions the gas molecules are very close together, so the fraction of space taken up by the molecules is substantial compared to the total volume

Assumptions about attractive forces:
Another assumption about gases is that when gas molecules are far apart there is very little interaction between the molecules
As the gas molecules become closer to each other intermolecular forces cause attraction between molecules
This reduces the number of collisions with the walls of the container
The pressure is less than expected by the ideal gas equation

Question 21

what is a standard solution?

Answer 21

one of a known concentration

Question 22

what is the molar concentration of a solution determined by?

Answer 22

the amount of solute (moles) and the volume of the solution

Question 23

define qualitative data

Answer 23

includes all non-numerical information obtained from observations, NOT from measurement

Question 24

define quantitative data

Answer 24

are obtained from measurements, and are always associated with random errors/uncertainties, determined by the apparatus and by human limitations such as reaction times.

Question 25

define accuracy

Answer 25

the closeness of the agreement between the result of a measurement compared with the true/literature value

Question 26

define precision

Answer 26

precision is the closeness of the agreement between different test measurements of the same quantity obtained by applying the same experimental procedure under the same conditions.

Question 27

formula for percentage uncertainty

Answer 27

absolute uncertainty/measured. value x100

Question 28

describe a random error

Answer 28

due to uncertainties associated with the apparatus used to make measurements/ by human limitations (ie reaction times) . cannot be eliminated

Question 29

describe a systematic error

Answer 29

due to faults in procedure or experimental design and cause a deviation in a particular direction. can be corrected/reduced

Question 30

when quantities with uncertainties are added or subtracted,

Answer 30

the absolute uncertainties are added

Question 31

when multiplying or dividing quantities with uncertainties,

Answer 31

percentage uncertainties should be added

Question 32

what is absolute uncertainty?

Answer 32

the margin of uncertainty associated with the result from a given measurement, ΔA

Question 33

what is relative uncertainty?

Answer 33

the ratio comparing the size of the absolute uncertainty to the size of the measured experimental result (A)

Question 34

give the equation for relative uncertainty

Answer 34

absolute uncertainty/measured experimental result

Question 35

ascorbic acid is C6H8O6; how many moles of carbon are there in 1 mol of ascorbic acid?

Answer 35

6

Question 36

relationship between volume and moles

Answer 36

v1/n1=v2/n2

Question 37

relationship between concentration and volume

Answer 37

C1V1=C2V2