lab

Question 1

what is an Erlenmeyer flask

Answer 1

used for titrations, are able to swirl the flask without spilling

Question 2

graduated cyclinders

Answer 2

used when the quantity does not need to be exact

Question 3

volumetric flask

Answer 3

used to make solutions

Question 4

top loading balance

Answer 4

sufficient for large quantities, use scopula attached to the bottle, but excess in waste container, push tare not cal, 2 dp

Question 5

analytical balance

Answer 5

4 dp, smaller quantities, close all 3 doors

Question 6

heating

Answer 6

small solution, 300 is sufficient (solution will not be 300)

Question 7

butane torches

Answer 7

point away from people, push knob firmly, turn up + if needed

Question 8

reading a burette

Answer 8

25 mL, units are 1.00, decimal place 0.10, curved meniscus shape

Question 9

titrating

Answer 9

don’t need to start at 0, stir after every addition, at endpoint solution should change color with addtion of one drop of titrant. one drop = 0.05 mL

Question 10

precipitation of a solid

Answer 10

heat solution to remove some solvent, add second solvent with low solubility, cool the solvent

Question 11

decanting

Answer 11

pouring off the liquid, a solid settles at the bottom of the container. pour slowly, can rid impurities by asking and adding another small amount of solvent and stirring

Question 12

drying solid

Answer 12

dry through vacuum, paper towel, oven, desiccator

Question 13

hot filtration

Answer 13

in paper funnel, pour some hot solution, the impurities will remain stuck on the funnel, only the pure solids will remain.

Question 14

vaccum filtration

Answer 14

suction filtration, uses buchner funnel

Question 15

pipetting

Answer 15

keep the tip of the pipette near the bottom, bulb is at teh top of the pipette, fill above meniscus, slip bulb off quickly with finger over it

Question 16

primary standard

Answer 16

determines concentration of a solution that cannot be made accurately.

Question 17

hydrated compound

Answer 17

has a specific # of water molecules associated with it as part of the crystal structure

Question 18

oxalic acid (white solid)

Answer 18

H2C2O4*2H2O, has two water molecules, associated through hydrogen bonding

Question 19

Copper II sulfate pentahydrate

Answer 19

CuSO45H2O, blue, 5 water molecules coordinated

Question 20

Anhydrous copper sulfate

Answer 20

CuSO4

white solid

Question 21

How does experiment 1 work?

Answer 21

During heating some water molecules are removed from hydrated compounds. While others decomposed before the water molecules are removed. mass % removed can be determined by heating sample to constant pass so it does nit decompose, and only the actual salt is left.

Question 22

What was the steps in experiment 1

Answer 22

1) find the mass of water removed = initial mass of sample-final mass of samle
2) mass % of water removed from hydrated compound = mass of water removed/ initial mass * 100
issues: warm objects warm the balance and crate air currents that destabilize the balance pan
the balance does not give stable value until it has cooled again

Question 23

Experiment # 2: synthesis of a coordination compound

Answer 23

ferrous ammonium sulfate hexahydrate is used in the first part if the experiment , (Fe(H2O)6)2+ is the conatined coordination complex, final compound: K3(fe(C2O4)s)*3H2O
The first reaction of the experiment oxalic acid provides the oxalate ions.

Question 24

steps in experiment 2

Answer 24

1) Ferrous ammonium sulfate and oxalic acid are reacted to produce iron (III) sulfate dihydrate. Note, if the liquid is not decanted a larger volume of solution, mostly water will be present at the end of the experiment leading to a lower yield
2) Fe(C2O4)*H2O is oxidized using excess hydrogen peroxide.
3) solution is hot filtered to remove excess reagents + insoluble impurities. Passed through a filtrate, to precipitate the product ethanol is added

Question 25

what is quantative analysis?

Answer 25

process used to detemine the amount of component in a sample

Question 26

what is gravimetric analysis?

Answer 26

a process that determines the mass change associated with a chemical or physical process determined.

Question 27

what is volumetric analysis?

Answer 27

measuring the volume of a solution required to completely react with another substance.. Ex. titration

Question 28

how does a titration work?

Answer 28

typically the reagent is the standard solution (ie, a solution with accurately known concentration). Then solution of reagent is gradually until all analyte has reacted and an equivalence point is reached. Equivalence point is observed by changes in the mixture’s colour signifying that the endpoint has been reached.

Question 29

how do you soften water?

Answer 29

exchange the Ca2+. and Mg 2+ for Na+, or add a chelating ligand like EDTA

Question 30

what is a complexometric titration

Answer 30

a solution containing metal ions is titrated with a solution of lewis bases such as EDTA 4-, forming a complex, must be carried out under basic conditions. in experment use a calmagite indicator that changes colour since it bonds weakly with metal ion, and changes colour once said ion is removed

Question 31

part 1 of experimental strategy experiment #4

Answer 31

uses gavrimetric determination of carbonate. 1) crush osyster shells and limestone. 2) mass of flask+ acid, mass of boat + sample, mass of boat, mass of flask + acid + sample at 20 minutes.

limestone, total mass % of carbonates: mcaco3 + mgcos/sample *100

oyster shell: mcacos/msample * 100

Note, oyster shell is almost pure CaCO3. and should be close to 100%.

Question 32

part 2: determining hardness of the water sample

Answer 32

measure as ppm of CaCO3, uses complexometric titrations.

calculations = mcaco3 (mg)/ vsample (L)

calgamite is the bidentate indicator used, blue signals the endpoint, solution is a red colour when the titration begins. (has a hydrolysis step titration at endpoint, meaning that the indicator reacts slowly). Color must persist for 30 seconds.

Titration : solution is 2 flasks with tap water and two flasks with mineral water, calgamite indicator added then EDTA in the burette

Question 33

what is qualitative analysis?

Answer 33

it is preformed to identify the substances it contains

Question 34

What was station 1 of experiment 4?

Answer 34

flame test: (works because all elements emit a colour when they are heated.) Na + = very strong bright, orange-yellow colour. Li= red-maroon streaks of coloured light, K+ = pale purple streaks of coloured light.

Question 35

hoe do you know if there are NH4+ ions present

Answer 35

Gasesous ammonia is formed from the reaction of ammoniaion ion and a weak base that will turn the red litmus paper blue. blue paper shows that your solution has NH4+ ions present.

Question 36

What was station 3 of experiment 4?

Answer 36

a) Cu(OH) (pale blue) reacts with NH3 to go to a intense deep blue solution of Cu(NH3)4 2+ ions
b) Zn(OH) is insoluble white solid that reacts with MHS to give colourless solution of Zn(NH3)4 2+ ions
c) Al(OH)3 is insoluble white solid that does not react with aqueous NH3, end with seperation and precipitate on the top.
d) Fe2+, Fe(OH)2 gives an insoluable green solution when NaOH is added (no NH3) used
e) Fe 3+, goes to Fe(OH)3 when NaOH is added and gives insoluble rusty brown solid

Question 37

how to test for Br- and I-

Answer 37

Chlorine water oxidizes Br- to Br2 which is soluble in the paraffin oil and gives a golden orange color.

Chlorine water oxidizes I- to I2 which is soluble in the paraffin oil and gives a purple colour.

Question 38

How do you test for the sulfate ion (SO4 2-)

Answer 38

Barium sulfate is insoluble white solid that remains insoluble in an acidic solution. The cloudy mixture stays cloudy after the acid is added.

Question 39

how do you test for carbonate ions

Answer 39

When carbonate ions (CO3 2- react with acid to from CO2 gas), you get small bubbles that quickly form in the solution. solution will fizz if there are CO3 2- ions

Question 40

how to test for chloride and fluoride ions

Answer 40

to test for chloride ion a white solid should appear. add your solution to AgNO3 if a white solid appears there are cl- ions (note if time had been given it would have turned purple with exposure to sunlight.

Ag+ and F- gives no reaction. (is soluable)

Question 41

How to test phosphate ions

Answer 41

if a phosphate ion is present (PO4)3-, it will form a bright yellow percipitate with ammonium molybdate (NH4)2MoO4 and strong acid (H+). (it fizzes and turns yellow)