topic 1/11 Flashcards
why do elements/compounds in a mixture retain their individual properties?
they are not chemically bonded together
explain the difference between a homogeneous and a heterogeneous mixture
Heterogeneous mixtures have visually distinguishable components, while homogeneous mixtures appear uniform throughout.
define a mole
a fixed number of particles referring to the amount, n, of substance
units for molar mass
g/mol
define molar mass
the ratio between the mass and the amount of substance (measured in moles)
difference between empirical and molecular formulae of compounds
simplest ratio vs actual number of atoms present in a molecule
what are standard temperature and pressure?
0 degrees celsius (273K) and 100kPa
what is true at standard temperature and pressure?
the molar volume of an ideal gas is 22.7 dm3/mol
give the equation for molar volume, as well as its usual value
volume (dm3)/ moles. 22.7
give the equation for the molar volume of an ideal gas and its usual value
22.7= vol/mol
what does 1 mol of gas contain?
6.02x10^23 atoms or molecules of the gas
state Avogadro’s law
equal volumes of any gas measured at the same temperature and pressure contain the same number of molecules
law for volume vs pressure
p=1/v
p1v1=p2v2
law for volume vs temperature
v is proportional to t (in K)
v1/t1=v2/t2
law for pressure vs temperature
p is proportional to t
p1/t1=p2/t2
combined gas law
p1v1/t1= p2v2/t2
ideal gas equation and units
pV=nRT
Pa for pressure
m3 for volume
K for temperature
R is the gas constant
describe the assumptions behind the kinetic theory of gases (5)
- 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
gases that follow the kinetic theory of gases are called
ideal gases
why do gases deviate from ideal behaviour at higher temperatures and pressures?
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
what is a standard solution?
one of a known concentration
what is the molar concentration of a solution determined by?
the amount of solute (moles) and the volume of the solution
define qualitative data
includes all non-numerical information obtained from observations, NOT from measurement
define quantitative data
are obtained from measurements, and are always associated with random errors/uncertainties, determined by the apparatus and by human limitations such as reaction times.
define accuracy
the closeness of the agreement between the result of a measurement compared with the true/literature value
define precision
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.
formula for percentage uncertainty
absolute uncertainty/measured. value x100
describe a random error
due to uncertainties associated with the apparatus used to make measurements/ by human limitations (ie reaction times) . cannot be eliminated
describe a systematic error
due to faults in procedure or experimental design and cause a deviation in a particular direction. can be corrected/reduced
when quantities with uncertainties are added or subtracted,
the absolute uncertainties are added
when multiplying or dividing quantities with uncertainties,
percentage uncertainties should be added
what is absolute uncertainty?
the margin of uncertainty associated with the result from a given measurement, ΔA
what is relative uncertainty?
the ratio comparing the size of the absolute uncertainty to the size of the measured experimental result (A)
give the equation for relative uncertainty
absolute uncertainty/measured experimental result
ascorbic acid is C6H8O6; how many moles of carbon are there in 1 mol of ascorbic acid?
6
relationship between volume and moles
v1/n1=v2/n2
relationship between concentration and volume
C1V1=C2V2
