Ch 1 Mole Concept Stiochometry

Question 1

What is isotopes

Answer 1

Isotopes are elements with the same atomic number but different mass number.

Question 2

What is relative isotopic mass Ar

Answer 2

It is the mass of 1 atom of the isotope relative to 1/12th the mass of 1 atom of 12^ C

Question 3

What is the relative atomic mass Ar

Answer 3

Ar of an element is the average mass of 1 atom of the element relative to 1/12th the mass of 1 atom of 12^ C.

Question 4

What is the relative molecular mass Mr

Answer 4

Mr of a substance is the average mass of 1 molecule of the substance relative to 1/12th the mass of 1 atom of 12^ C

Question 5

Relative formula mass Mr

Answer 5

Mr of a substance is average mass of 1 formula unit of the substance relative to 1/12th the mass of 1 atom of 12^ C

Question 6

What is One mole of a substance

Answer 6

it contains exactly 6.02 x 10^23 elementary entities

Question 7

What is molar mass

Answer 7

Molar mass is the mass per 1 mol of substance

Question 8

molar concentration formula

Answer 8

amount (mol) = concentration (mol/dm3) x volume(dm3)

Question 9

conc g/dm3 formula

Answer 9

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

Question 10

combustion of hydrocarbon

Answer 10

CxHy + (x + y/4) O2 ->
xCO2 + y/2 H2O

Question 11

during dilution what remains the same

Answer 11

amount of solute

Question 12

define empirical formula

Answer 12

it is the simplest whole ratio of the elements present in 1 molecule or formula unit of the cpd

Question 12

define molecular formula

Answer 12

it is the actual number of each of the different atoms present in the molecule

Question 13

Ar and Mr to what dp

Answer 13

1dp

Question 14

2 examples of redox reactions

Answer 14

disproportionation rxn
(same element oxi and red)
comproportionation rxn
(two reactant same element with diff oxi number reach same oxi number)

Question 15

balancing redox eqn acronym acidic medium

Answer 15

E O H C
elements
oxygen (h2o)
hydrogen (H +)
charge (electrons)

Question 16

balancing redox extra steps for basic medium

Answer 16

neutralise H+ with OH-
combine to form H2O
cancel out common terms

Question 17

thiosulfate + iodine eqn
describe colour

Answer 17

2 S2O3 ^2- (colourless) +
I2 (brown) ->
S4O6 ^2- (colourless) +
2 I – (colourless)

all aq

Question 18

why is starch solution added to iodine

Answer 18

brown fade to pale yellow
starch solution make end point colour change more obv, form a dark blue iodine-starch complex