Stoichiometry

Question 1

define relative isotopic mass

Answer 1

relative isotopic mass of an isotope is the number of times the isotope is heavier than 1/12 the mass of an atom of carbon-12

Question 2

define isotopes

Answer 2

isotopes are atoms of the same element, with the same number of protons but different number of neutrons

Question 3

define relative atomic mass (Ar)

Answer 3

Ar of an element is the average mass of its atoms in the isotopic mixture, compared to 1/12 the mass of an atom of carbon-12

Question 4

define relative molecular mass (Mr)

Answer 4

Mr of a molecule is the average mass of the molecule compared to 1/12 the mass of an atom of carbon-12

Question 5

define relative formula mass

Answer 5

relative formula mass of an ionic compound is the sum of Ar of each elements

Question 6

define Mole

Answer 6

one mole of a substance contains exactly 6.02 x 10^23 elementary entities

Question 7

define molar mass of a substance

Answer 7

molar mass of a substance refers to the mass of one mole of it

Question 8

Avogadro’s constant = ?

Answer 8

6.02 x 10^23 mol^-1

Question 9

state Avogadro’s law

Answer 9

Avogadro’s law states that equal volumes of all gases under the same conditions of temperature and pressure contain the same number of atoms/molecules

Question 10

define molar volume of a gas

Answer 10

molar volume of a gas is the volume occupied by 1mol of it (note: different molar volume for stp and rtp)n

Question 11

define concentration of a solution

Answer 11

the concentration of a solution is measured by the amount of solute contained in a given volume of solution

Question 12

what is a standard solution

Answer 12

a standard solution is a solution with a known amount of solute in a given volume of the solution

Question 13

relate concentration in mol/dm3 to concentration in g/dm3

Answer 13

conc in g/dm3= conc in mol/dm3 x molar mass (g/mol)

Question 14

define dilution

Answer 14

dilution is the process of adding solvent to a known volume of solution so as to lower the concentration, with the same amount of solute remaining after dilution (C0V0=CdVd)

Question 15

define empirical formula

Answer 15

empirical formula gives the simplest ratio of the number of atoms of each element present in the compound

Question 16

define molecular formula

Answer 16

molecular formula gives the actual number of the number of atoms of each element present in the compound