Atoms and Reactions Flashcards
(23 cards)
Define relative atomic mass
the weighted mean mass of an atom of an element compared to 1/12th of the mass of an atom of Carbon - 12
Define relative isotopic mass
the mass of an atom of an isotope compared with 1/12th of the mass of an atom of Carbon - 12
Which of relative atomic mass and relative isotopic mass has to be written as a whole number?
Relative isotopic mass must be given as a whole number
Define relative molecular mass (Mr)
the average mass of a molecule or formula unit compared to 1/12th of the mass of an atom of Carbon - 12
How do you calculate relative atomic mass (Ar)?
Multiply each relative isotopic mass by its percentage relative isotopic abundance.
Add these results up
Divide the total by 100 (the total of the abundances)
What do the x-axis and y-axis on a mass spectra represent?
The x-axis represents the mass to charge ratio (m/z), you can assume this is equal to the relative isotopic mass
The y-axis represents the abundance of ions often as a percentage
What is the mole (mol) a measure of?
The amount of substance
What is Avogadro’s Constant?
The number of particles in one mole.
6.02 x 10^23
What is the molar mass?
The mass of one mole of a substance (often in grams) (the same as the relative molecular mass)
What formula relates mass, moles and molar mass?
Moles = mass / molar mass
What is the molar gas volume?
The volume/space that one mole of a gas occupies at a certain temperature and pressure. It has units dm^3mol^-1.
What is the molar gas volume of any gas at room temperature and pressure?
24dm^3mol^-1
What is the ideal gas equation (and what does each symbol represent)?
pV=nRT p: pressure (Pa) V: volume (m^3) n: number of moles (mol) R: gas constant, 8.314 (JKmol^-1) T: temperature (K)
How do you convert kPa to Pa?
1kPa = 1000Pa
How do you convert degrees celsius to kelvin?
Add 273
1C = 274K
Define empirical formula
The smallest whole number ratio of atoms of each element in compound,
Define molecular formula
The ratio of the actual number of atoms of each element in a compound
A molecule has an empirical formula of C4H302 and a molecular mass of 166gmol^-1. Work out its molecular formula.
Empirical mass = 83.0gmol^-1
166/83.0 = 2
C4H302 x 2 = C8H6O4
Answer = C8H6O4
How do you calculate empirical formula?
Calculate the moles of each element within the compound using the mass or percentage by mass.
Divide each mole value by the smallest calculated mole value (then round these value to get sensible numbers)
Form a ratio and use the ratio to display the empirical formula.
What is the name of any ion excluded from an ionic equation?
Spectator Ion
How is an ion formed?
When electrons are transferred from one atom to another
What is the charge of a nitrate ion? (NO3)
1-
What is the charge of a carbonate on? (CO3)
2-
