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Question 1

what does Avogadro’s constant represent?

Answer 1

the number of atoms per mole of the carbon-12 isotope

Question 2

how do you calculate the mass of 1 mole of an element?

Answer 2

mass of 1 mole = relative atomic mass in grams

Question 3

equation linking moles, mass and mr?

Answer 3

moles (mol) = mass (g) / molar mass (g mol-1)

Question 4

what is an empirical formula?

Answer 4

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

Question 5

how do you calculate empirical formula?

Answer 5

set mass to percentage, vice versa (must add to 100)
divide the amount of each element by its mr
divide the answers by the smallest value obtained
ratio!

Question 6

what is Avogadro’s law?

Answer 6

under the same temperature and pressure, one mole of any gas would occupy the same volume

Question 7

how much volume does a gas occupy at room temp and pressure?

Answer 7

24 dm3 or 24000 cm3

Question 8

molar gas volume

Answer 8

the volume per mole of gas molecules

Question 9

why do different gas particles occupy the same volume?

Answer 9

the gas particles are very spread out, hence the individual differences has no effect

Question 10

how do you calculate moles when gas volume is given?

Answer 10

moles = volume (dm3) / 24
moles = volume (cm3) / 24000

Question 11

what are the ideal ways in which gases behave?

Answer 11

continuous motion
no intermolecular forces experienced
exert pressure when they collide with each other or container
no kinetic energy lost in collisions
when temp increases, kinetic energy of gases increase

Question 12

ideal gas equation and units

Answer 12

pV = nRT
pressure (Pa)
volume (m3)
temperature (K)

Question 13

1 atm = ? Pa

Answer 13

1 atm = 101325 Pa

Question 14

how do you convert from *C to K?

Answer 14

+ 273

Question 15

what does concentration of a solution mean?

Answer 15

amount of solute dissolved in 1 dm3 of solvent

Question 16

equation linking moles, conc and volume

Answer 16

moles = concentration (moles dm-3) x volume (dm3)

Question 17

what is a standard solution?

Answer 17

a solution of known concentration

Question 18

how do you prepare a standard solution?

Answer 18

1 weigh solute using weigh by difference method
2 dissolve solute in beaker using the solvent
3 pour solution into volumetric flask
4 rinse the beaker using the solution (e.g. distilled water) and add to flask
5 add solvent to flask until it reaches graduation line
6 mix solution thoroughly

Question 19

concentrated
dilute

Answer 19

concentrated - large amount of solute per dm3 of solvent
dilute - small amount of solute per dm3 of solvent

Question 20

percentage yield definition

Answer 20

efficiency of which reactants are converted into products

Question 21

why might the percentage yield not be 100%?

Answer 21

reaction may be at equilibrium
reactants may be impure
side reactions could happen
reactants or products may be left behind when transferring
loss of products during separation and purification

Question 22

percentage yield equation

Answer 22

percentage yield = actual amount of product (mol) / theoretical amount of product (mol) x 100

Question 23

atom economy?

Answer 23

proportion of desired products compared with all the products formed in the reaction

Question 24

atom economy equation?

Answer 24

atom economy = mr of desired product / sum of the mr of all products x 100

Question 25

does 100% yield = 100% atom economy?

Answer 25

no, even if all the reactants are converted into products, not all products of the reaction will be required products

Question 26

what type of reaction has 100% atom economy?

Answer 26

addition reactions (two or more reactants combined to form one product)

Question 27

systematic error

Answer 27

same error appears in each measurement

Question 28

what is the weighing by difference method?

Answer 28

1 measure mass of container
2 add chemical to container and weigh container
3 calculate mass of the chemical
4 transfer chemical and reweigh empty container
5 calculate the mass of chemical transferred

Question 29

maximum error formula

Answer 29

uncertainty / total volume x100
e.g. 0.2 / 250 x 100 = 0.08%