Amount of Substance Flashcards
what is relative atomic mass?
the mean weighted mass of one atom of an element on a scale chosen so that the mass of the carbon-12 isotope is exactly 12
what is relative isotopic mass?
the mass of one atom of a specific isotope of an element on a scale chosen so that the mass of the carbon-12 isotope is exactly 12
what is relative molecular mass?
the mean weighted mass of one molecule of a compound on a scale chosen so that the mass of the carbon-12 isotope is exactly 12
what is a mole?
an amount of substance containing exactly 6.02×10^23 elementary particles
how do you calculate moles of pure substances?
n = mass / Molar mass
how do you calculate numbers of particles?
particles = n x NA
how do you calculate moles in solutions?
n = (concentration x volume) / 1000
how do you change from dm3 to cm3?
x1000
how do you calculate moles of gases?
n = v / 24 (dm3)
or
n = v / 24,000 (cm3)
what is the ideal gas equation?
pV=nRT
how do you convert temperatures to Kelvins?
+273
how do you convert from m3 to cm3?
x1,000,000
how do you calculate % yield?
(actual mass/moles made / theoretical mass/moles) x 100
how do you calculate atom economy?
(total formula mass of wanted product in equation / total formula masses of all products) x 100
what are systematic errors?
errors that are consistently wrong due to an inherent problem in the process (eg- zero errors)
what are random errors?
errors caused by uncertainty in the value of any data collected due to limitations in reading the apparatus
how do you calculate % error?
((maximum error in one reading x number of readings) / amount of variable measured) x 100
how can you reduce uncertainty?
- use equipment with smaller graduations (more decimal places)
- increase value of mass / volume
