amount of substances (phys I)

Question 1

simple molecular elements written as a formula

Answer 1

*most have a 2 written after the symbol eg. H2, K2, Cl2
*phosphorus = P4, sulfur = S8

Question 2

metal + acid —>

Answer 2

salt + hydrogen

Question 3

metal oxide/hydroxide + acid —>

Answer 3

salt + water

Question 4

metal carbonate/hydrogencarbonate + acid —>

Answer 4

salt + water + carbon dioxide

Question 5

ammonia + acid —>

Answer 5

ammonium salt

Question 6

metal + water —>

Answer 6

metal hydroxide + hydrogen

Question 7

thermal decomposition of a metal carbonate —>

Answer 7

metal oxide + carbon dioxide

Question 8

1 ton =

Answer 8

1,000,000g

Question 9

1 ton =

Answer 9

1,000,000g

Question 10

carbonate

Answer 10

CO3

Question 11

hydride

Answer 11

h

Question 12

formula for hydrochloric acid

Answer 12

HCl

Question 13

formula for sulfuric acid

Answer 13

H2SO4

Question 14

formula for nitric acid

Answer 14

HNO3

Question 15

formula for phosphoric acid

Answer 15

H3PO4

Question 16

empirical formula

Answer 16

•mass (My)
•big no. (Butt)
•divide (Didn’t)
•smallest (Size)
•divide (Down)

Question 17

moles =

Answer 17

mass/Mr

Question 18

no. of particles =

Answer 18

no. of moles x (6.023 x 10^23)

Question 19

calculating max. theoretical mass

Answer 19

1) calculate no. of moles of substance with known mass (mass/Mr) —> dont incl. big numbers
2) use stoichiometric numbers to get molar ratio & multiply by no. of moles (s. no. of desired substance on top of fraction)
3) multiply no. of moles by Mr of desired substance

Question 20

% A.E =

Answer 20

• (mass of desired product/mass of total products) x 100
• include stoichiometric no.s

Question 21

% yield =

Answer 21

(mass of product obtained/max. theoretical mass of product) x 100

Question 22

reasons for yield being lost

Answer 22

• reaction is reversible
• some reactants may react in side reactions
• reaction may not have gone to completion —> heat to constant mass!

Question 23

density =

Answer 23

mass / volume

Question 24

Ideal Gas Equation

Answer 24

pV = nRT
*p in Pa
*V in m^3
*R is 8.31 J/mol/K
*T in Kelvins

Question 25

converting to Kelvin

Answer 25

temp in celsius + 273

Question 26

converting to Pa

Answer 26

•mPa x 1000 = kPa
•kPa x 1000 = Pa
Martin —> martin multiplies
Kicked
Pam

Question 27

converting to m^3

Answer 27

cm^3 /1000 = dm^3
dm^3 /1000 = m^3
Cool
Dinosaurs —> dinosaurs divide
Mew

Question 28

concentration =
(mol/dm^3)

Answer 28

moles / volume (dm^3)

Question 29

concentration =
(g/dm^3)

Answer 29

conc. (mol/dm^3) / Mr
>mol/dm^3 also means molarity
>mass = moles/Mr

Question 30

MGV (molar gas volume) equation

Answer 30

no. of moles = given volume (dm^3) / mgv

Question 31

molar volumes of gas (expl.)

Answer 31

-if temp & pressure are at standard values, molar volumes of gas can be determined
*standard temp = 273k
*standard pressure = 101300Pa (101.3kpa)

Question 32

mgv at standard & room temp

Answer 32

*standard temp mgv —> 22.4 dm^3
*room temp mgv —> 24dm ^3

Question 33

method —> volumetric solution

Answer 33

1) weigh sample bottle containing the solid (on 2dp balance)
2) transfer solid to beaker & reweigh sample bottle
3) record difference in mass
4) add distilled water & stir with glass rod until all solid dissolved
5) transfer to a volumetric flask with washings
6) make upto the 250cm^3 mark w distilled water
7) shake flask

Question 34

errors —> volumetric solution

Answer 34

*if using anhydrous NaHSo4, ensure it isn’t too old —> it’ll have picked up water —> mass values incorrect
*systematic error of balance —> gives it to 0.01g —> use more acc. balance or calculate diff in mass
*hard to see meniscus behind dark liquid —> place white paper behind

Question 35

method —> titration

Answer 35

1) pour approx. 100cm^3 known conc. sol. into beaker
2) fill burette with this sol.
3) pour approx 100cm^3 unknown conc. sol. into 2nd beaker
4) use pipette & pipette filler to transfer 25cm^3 of unknown conc. sol. into conical flask
5) add phenolphthalein indicator to conical flask
6) record initial burette reading
7) add sol. in burette to c. flask until permanent colour change —> record final burette reading & calculate change in volume in burette (titre vol.)
8) repeat for 2 concordant results

Question 36

…protic acids

Answer 36

-monoprotic acid = 1H —> molar ratio is 1:1
-diprotic acid = 2H —> molar ratio is 1:2
-triprotic acid = 3H —> molar ratio is 1:3

Question 37

calculating concentration from a titration

Answer 37

1) use vol. & conc. of 1 reactant to calculate moles (M=CxV)
2) molar ratio x moles
3) calculate needed conc. of reactant

Question 38

vol. unit needed for conc. of titration

Answer 38

dm^3