Stoichiometry

Question 1

1 mole =

Answer 1

6.023 x 10ˆ23 atoms

Question 2

Molar mass

Answer 2

Mass of one mole of atoms; measured in gmolˆ-1

Question 3

Formula for moles

Answer 3

n = m/M

Question 4

Does conservation of moles and mass occur?

Answer 4

yes

Question 5

Limiting reactant/reagent

Answer 5

When one reactant runs out before the other, and the reaction will stop. Other reactant said to be in excess

Question 6

What limits the amount of products produced and the ratio of moles?

Answer 6

Limiting reagent

Question 7

Concentration of a solution

Answer 7

amount of solute dissolved per volume of a solvent (mol Lˆ-1)

Question 8

Concentration formula

Answer 8

c = n/V

Question 9

Which equation helped to make fertilisers for plants and hence increase the population?

Answer 9

N2 + 3H2 –> 2NH3

Haber reaction

Question 10

What is a solution?

Answer 10

Homogenous mixture of two or more substances

Question 11

What is an electrolyte?

Answer 11

Substances whose aqueous solutions produce ions. Most likely a ionic compound. Few molecular substances solvate eg ACIDS

Question 12

What is a non-electrolyte?

Answer 12

Substances whose aqueous solutions don’t have ions. Most likely a molecular compound.

Question 13

Dissociation

Answer 13

In water, the elctronegative dipoles seperate ions of ionic compounds –> Solvated

Solvation stablises ions in sol, prevents ions from recombining and ions are free to move so they disperse uniformly

Question 14

Strong/weak electrolytes

Answer 14

Strong completely dissociate but weak doesn’t it, some remain as molecules.

Solubility doesn’t say how dissociative. Some can be highly soluble but take time to dissociate and vice versa.

Question 15

Chem equilibrium

Answer 15

determines relative no. of ions and neutral particles and they are constant

Question 16

Stoichiometry

Answer 16

Concerned with the relative amounts of ps and rs, comes from the greek words “element” and “o measure”

Question 17

How to solve a stoichiometry question?

Answer 17

Mass –> moles –> moles after changes in ratio –> mass

Question 18

How to find the moles of individual elements in a compound?

Answer 18

If product is given, use their numbers eg CH4N2O

• 1 mol of C
• 4 mols of H
• 2 moles of 2
• 1 mol of O

Question 19

To start the equation…

Answer 19

solve for sum of reactants = sum of products and that the eqs are balanced

Question 20

Another word for c

Answer 20

Molarity or M

Question 21

Going from reactant mols –> product mols

Answer 21

Adjust to the ratio, other way then follow the ratio

Question 22

How to find the LR

Answer 22

Compare to set eq using the moles provided in question. To find product moles, use the limiting reactant.

Question 23

Excess reactant?

Answer 23

Find how much of the limiting reactant’s moles were used. Same amount of excess will be used. ER - LR = excess amount

Question 24

To find moles between reactants?

Answer 24

Set ratio, 1:1 or use percentage method i.e compare moles to set eq and see how much percentage reduction it was