amount of substance

Question 1

what is the relative atomic mass

Answer 1

the mean mass of an atom of an element, divided by one twelfth of the mean mass of an atom of the carbon-12- isotope

Question 2

what is the relative molecular mass

Answer 2

the mean mass of a molecule of a compound, divided by one twelfth of the mean mass of an atom of the carbon-12 isotope.

Question 3

what is the relative formular mass

Answer 3

it is the same as the Ar and Mr but for ionic compounds

Question 4

what are the two equations to find mols

Answer 4

Mr x mol = mass
mol= conc/vol

Question 5

what are the trends gasses and volatile liquids follow under standard conditions

Answer 5

-pressure is proportional to temperature
-volume is proportional to temperature
-pressure and volume are inversely proportional

Question 6

what is the ideal gas equation
and what re the units of each

Answer 6

pV=nRT
p=pressure in pascals
V=volume in m^3
T=temperature in Kelvin
n= moles
m= mass in grams
R=ideal gas constant

Question 7

what is the empirical formular

Answer 7

the simplest whole number ratio of atoms of each element in a compound

Question 8

what is the molecular formular

Answer 8

the true number of each atom in the molecule

Question 9

what is the atom economy

Answer 9

a measure of what proportion of the products of a reaction are the desired product and how much is waste. the higher the atom economy the less waste produced

Question 10

what is formular for atom economy

Answer 10

molar mass of wanted products from equation/ total molar mass of products from equation x100

Question 11

what is the percentage yield

Answer 11

the mass we would theoretically make vs what we actually make

Question 12

what is the formular for percentage yield

Answer 12

mass of product obtained/ maximum theoretical mass of product x100

Question 13

why is a higher atom economy better

Answer 13

a higher atom economy mean less waste meaning it is more economically viable and better for the environment as less recourses needed

Question 14

what are spectator ions and why are they not in ionic equations

Answer 14

in reaction involving ionic compounds dissolving in water some ions may not be involved in the reaction. these are called spectator ions. for such reasons we can write ionic equations that only shows the species that are involved in the reaction.

Question 15

what are the main steps to prepare a 250cm^3 standard acid solution

Answer 15

-gather equipment (volumetric flask, beaker, pipette, glass rod, goggles, funnel, weighing boat)
-use a table to record weight or weighing boat the with acid as well and finally acid alone
-dissolve acid in distilled water then add to volumetric flask with washings
-fill flask with distilled water up too line using pipette
-flip three time to fully mix

Question 16

define the mole

Answer 16

the amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon 12

Question 17

how do you convert 0C to kelvin

Answer 17

add 273

Question 18

how can you find the number of particles

Answer 18

moles of substance Avogadro’s constant

Question 19

what safety precautions should you take when dealing with a toxic gas

Answer 19

keep it n a fume cupboard to prevent toxic gas getting out

Question 20

how could you reduce the percentage uncertainty in using a burette

Answer 20

decrease the concentration of the acid or alkali in the burrette so you need more to neutralise the acid or alkali reducing the percentage uncertainty