Amount Of Substance

Question 1

mole definition

Answer 1

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

Question 2

relative atomic mass definition

Answer 2

average mass of an atom of one element compared to 1/12th of the mass of an atom of carbon 12

Question 3

relative molecular mass definition

Answer 3

the average mass of a molecule compred to 1/12th the mass of one atom of carbon 12

Question 4

avogadro’s constant

Answer 4

6.022x10^23

Question 5

One mole of any specified entity contains ______ of that entity

Answer 5

6.022x10^23

Question 6

moles =

Answer 6

mass/mr

Question 7

PV =

Answer 7

nRT

Question 8

units for
P
V
n
T

Answer 8

Pa
m^3
mol
K

Question 9

concentration=

Answer 9

moles/volume

Question 10

cm3 to dm3?

Answer 10

x10^-3

Question 11

cm3 to m3?

Answer 11

x10^-6

Question 12

dm3 to m3?

Answer 12

x10^-3

Question 13

°C to K?

Answer 13

+ 273

Question 14

1 tonne in kg?

Answer 14

1000kg

Question 15

number of particles=

Answer 15

moles of substance x avogadros constant

Question 16

density =

Answer 16

mass/volume

Question 17

method for empirical formula?

Answer 17

divide each mass/%mass with the atomic mass of the element
for each, divide by the smallest number out of all of them
multiply if necessary for whole numbers

Question 18

3.51g of hydrated zinc sulfate were heated and 1.97g of anhydrous zinc sulfate were obtained.
Calculate the integer x’s value in ZnSO4.xH2O.

Answer 18

Calculate the mass of H2O = 3.51-1.97 = 1.54g

calculate moles of ZnSO4 = 1.97/161.5 = 0.0122

calculate moles of H2O = 1.54/18 = 0.085

calculate mole ratio of ZnSO4 to H2O:
0.0122/0.0122 = 1 ZnSO4
0.085/0.0122 = 7 H2O

X= 7

Question 19

Dilution conc equation if moles does not change

Answer 19

new diluted conc= original conc x original volume/new diluted volume

Question 20

Potential errors in using a gas syringe

Answer 20

gas escapes prior to bung insertion
syringe sticks
some gases like CO2/SO2 are water soluble so actual amount of gas not measured

Question 21

P1V1 =

Answer 21

P2V2 if temperature and moles is constant

Question 22

percentage yield =

Answer 22

(actual yield in mol/ theoretical yield in mol) x 100

Question 23

percentage atom economy =

Answer 23

(mr of all useful products/ mr of all reactants) x 100

Question 24

How to deal with acid spills

Answer 24

Add CaCO3 to neutralise spills
Not corrosive
No hazard caused if in excess

Question 25

Uncertainty of a reading (1 judgement) is at least …

Answer 25

+-0.5 of the smallest scale reading

Question 26

Uncertainty of a measurement is at least …

Answer 26

+- 1 of the smallest scale reading

Question 27

maximum total percentage apparatus uncertainty=

Answer 27

((uncertainty/measurement made on apparatus) x100) for each piece of equipment

Question 28

How to reduce titre uncertainties?

Answer 28

increasing conc/vol of substance in conical flask
decreasing conc/vol of substance in burette

makes titre larger

Question 29

How to reduce mass measurement uncertainties?

Answer 29

Using a balance that measures to more decimal places
Using a larger mass

Question 30

If % uncertainty due to apparatus < % difference between the actual value and the calculated value …

Answer 30

there is a discrepancy in the result due to other errors

Question 31

if the % uncertainty due to appratus > percentage difference between the actual value and calculated value …

Answer 31

there is no discrepancy in the result
all differences between values can be explained by equipment sensitivity