Amount of Substance

Question 1

Outline the method for a forming a standard solution for a titration.

Answer 1

1- weigh sample bottle + solid then transfer solid to a beaker. Reweigh bottle and find difference in mass to find true mass of solid being used in titration

2-add 100cm3 of distilled water to beaker. Stir with a glass rod until all of solid has dissolved.

3-transfer solution to a volumetric flask (using a funnel) with WASHINGS. Make solution up to 250cm3 and mix well. When making solution up to 250cm3, bottom of the meniscus should be touching 250cm3 mark.

Question 2

What is the ideal gas equation? What are the units required?

Answer 2

PV=nRT

P- pressure in Pa
V- volume in m3
n- number of moles of gas
R- 8.31 J K-1 mol-1
T- temperature in K

Question 3

What is the Avogadro Constant?

Answer 3

The number of atoms in 12g of C12.

1 mole= 6.022 x 10^23 particles.

Question 4

What are Concordant results?

Answer 4

Results that are within 0.1 of each other.

Question 5

How can you find concentration in g dm-3?

Answer 5

Mr x Concentration in mol dm-3

Question 6

How can percentage error be reduced in a titration?

Answer 6

Use a larger titre volume.

Question 7

What is 1m3 in cm3?

Answer 7

1,000,000cm3.

Question 8

What is 1m3 in dm3?

Answer 8

1,000dm3

Question 9

What is 273K in Celsius?

Answer 9

O degrees C

Question 10

What is 1kPa in Pa?

Answer 10

1,000Pa

Question 11

Define empirical formula.

Answer 11

Simplest number ratio of atoms of each element in a compound.

Question 12

Define molecular formula.

Answer 12

Actual number ratio of atoms of each element in a compound.

Question 13

How can you calculate empirical formula?

Answer 13

• Mass or Percentage of each element
• divided by its Ar
• then divide each number by the smallest value from the previous calculation
• repeat until you get a whole number ratio

Question 14

Equation for % yield?

Answer 14

(amount of specific product formed / theoretical maximum of product that could be formed) x100

Question 15

What is the relative atomic mass (Ar)?

Answer 15

(average mass of 1 atom of an element / 1/12th the mass of a C12 atom)

Question 16

What is the Mr of a compound?

Answer 16

(average mass of 1 molecule / 1/12th the mass of a C12 atom)

Question 17

How can you calculate concentration?

Answer 17

moles / volume

Question 18

How can you calculate moles of an element or compound?

Answer 18

mass in g / Mr or Ar

Question 19

How can you calculate Atom Economy?

Answer 19

(Mr of desired products / Total Mr of all products) x 100