EL 9

Question 1

what is stoichiometry and what does it tell you

Answer 1

amount of substances that are involved in a chemical reaction
tells you-
quantities of reactants needed to produce required quantity of product
quantities of products produced from a known quantity of reagents

Question 2

what equation is used to work out reacting masses

Answer 2

n = m/Mr m
Mr n

Question 3

what equation is used to work out the concentration of solution

Answer 3

concentration in mol dm-3 = concentration in gdm-3/molar mass

Question 4

what gas is released when acids react with carbonates

Answer 4

CO2

Question 5

what is an oxonium ion and where are they found

Answer 5

found in every solution of acid in water
act as an acid, donate H+ ions and turn back into H2O
e.g.
HCL(aq) + H20(l)
[]
H30+(aq) + Cl-(aq)

Question 6

what is a titration used for

Answer 6

to find concentrations of acids or bases
solution of unknown concentration is reacted with a solution with a known concentration to find unknown

Question 7

how to set up a titration

Answer 7

use a pipette and add measured volume into a conical flask
place other solution into burette
attach a clamp stand and place a white tile underneath

Question 8

how to carry out a titration

Answer 8

1.read and record the initial volume in burette (cm3)
- read from meniscus at eye level
- must be recorded at 2 decimal places
- last digit must be 0 or 5
2. place a few drops of indicator into the conical flask
- indicator will change colour as reaction occurs
3. run solution from burette into the conical flask
-swirl flask as solution is added
-stop titration when colour change happens
- read final volume on burette and work out the difference between initial - final volume (in cm3 and is called the volume of titre used)
4. repeat titration until at least 3 titres are within 0.10cm3 if each other then calculate the mean average

Question 9

what equation is used to calculate the concentration

Answer 9

n = C x V n
C V