What is the objective (purpose) of each part of the ANC of antiacid tablets experiment? (2)

Part A finds the amount of ~1M HCl remaining after a reaction with an antiacid tablet with an unknown ANC. Part B uses an antiacid tablet with a known ANC to determine the concentration of the ~1M HCl solution in a process called standardization.

Name and define the specific method used in each part of the ANC of antiacid experiment. (2)

Back titration in part A: Where the basic thing (the antiacid tablet) is dissolved in an acid and that solution serves as the analyte meanwhile a base is the titrant.

Standardization in part B: Where the concentration of a solution (HCl) is found.

Why is back titration used specifically for Part A of the ANC of the antiacid experiment? two reasons (2)

The antiacid tablet dissolves better in acid than water and back titration prevents the base from neutralizing with exposure to air.

What two indicators are used in this experiment? List their colour changes.

Bromocresol green (yellow to blue in basic conditions) and phenolphthalein (clear to pink in basic conditions)

The stomach contains an acid similar to what solution?

0.1M HCl

The antiacid tablets will be dissolved in what acidic solution? (be specific about conentration)

0.1M HCl

What do ANC and RO stand for?

Acid neutralizing capacity, reverse osmosis

What is the decomposition equation for carbonic acid?

H₂CO_{3 (aq)}-->H₂O_(l)+CO_{2 (g)}

When you dilute a solution what changes and what is constant?

The volume changes but the number of moles stays constant.

When preforming a dilution does one add the entire amount of solute or solvent to the volumetric flask?

The entire amount of solute.

Describe the steps you would take with a clean new burette until it is charged full of your titrant. (2)

1. Make sure stop is closed.
2. Several mLs of your titrant solution into the burette
3. Cap top with thumb and roll burette so titrant covers all the surface
4. Titrant out through stop
5. Fill burette with titrant

In the manual you are told the HCl is ~1M. Why is it necessary to standardize the solution?

The HCl must be standardized so we can determine the difference in H⁺ before and after adding the antiacid tablet, aka. the ANC of the antiacid tablet.

Why is it necessary to dilute the stock HCl solution before titrating it with ~0.1M NaOH?

The HCl was ~1.0M meaning there are roughly 10 times as many HCl moles as ~0.1M NaOH. You would need to add a lot of NaOH to get to the end point thus, diluting the HCl allows you to use less NaOH solution.

Define the terms equivalence point and end point.

Equivalence point: Equal amounts of acid and base, End point: indicator changes colour

What are the objectives for the three phases of a synthesis (reaction, workup, characterization) in the multiweek redox titration?

Reaction: Sythesize a sample of potassium trioxalatoferrate (III) trihydrate

Workup: Isolate the potassium trioxalatoferrate (III) trihydrate crystals

Characterization: Confirm molarities and concentrations inside sample

Name this compound: K₃[Fe(C₂O₄)₃]*3H₂O

Potassium trioxalatoferrate (III) trihydrate

What is the chemical formula for ferrous oxalate dehydrate and what colour is it?

FeC₂O₄*2H₂O, mustard yellow

Is oxalic acid a liquid or solid under normal lab conditions?

Solid

What colour occurs at the end of the permanganate - oxalate reaction in the multiweek synthesis and redox titration?

A faint pink (phenolphthalein indicator)

Why should potassium permanganate be handled carefully?

If it gets on clothes or skin it will reduce and leave brown stains.

What is the catalyst used in the potassium permanganate - oxalate reaction?

Mn²⁺ (Manganous ion)

What colour are the crystals of K₃[Fe(C₂O₄)₃]*3H₂O?

Radioactive green

Why did you analyze the crystals of K₃[Fe(C₂O₄)₃]*3H₂O?

To confirm that they have an appropriate amount of each ion. This also confirms their purity.

In qualitative analysis of cations which ions are in the silver group (group 1)? (4)

Ag+, Hg₂2+, Tl+, Pb2+

In qualitative analysis of cations which ions are in the copper group (group 2)? (5)

Hg2+, Bi3+, Cu2+, Sn2+, Sn4+

In qualitative analysis of cations which ions are in the zinc-aluminium group (group 3)? (6)

Zn2+, Fe2+, Fe3+, Ni2+, Cr3+, Al3+

What do group 1 cations precipitate as?

Chlorides

WHat do group 2 cations precipitate as?

Sulfides

What do group 3 cations precipitate as?

Sulfides and hydroxides

Adding what precipitates the group 1 cations? (concentration and species)

6M HCl

Adding what precipitates the group 2 cations? (concentration, species, pH)

0.1M H₂S, pH of 0.5

Adding what precipitates the group 3 cations? Why is further discrimination possible with them? (2 species, concentration for 1, pH)

NaOH and 0.1M H₂S and a pH of 9. NiS and ZnS won't redissolve if layered with 10^-2 M acid.

All the group 1 cations precipitate as what colour?

White

In the confirmatory test for lead what colour are you looking for? What colour might be masking it?

Yellow, orange

In the confirmatory test for silver and mercury what differences in reactions are you looking for?

Most or all the precipitate dissolving (AgCl) or the precipitate becoming black or grey (Hg₂ ²⁺) with the addition of 6M NH₄OH.

In the confirmatory test for mercury (Hg²⁺, not Hg₂ ²⁺ this time) what are you looking for when you immerse a piece of copper wire in your solution?

A shiny deposit of mercury on wire as it is reduced

In the confirmatory test for bismuth what colour are you looking for when adding the sodium stannite to reduce the bismuth?

jet black

In the confirmatory tests for copper what are the two possible indicators of a positive test?

The presence of a dark precipitate in a heated solution or the appearance of a maroon precipitate.

What colour are you looking for in the confirmatory test for Cadmium?

Yellow

In the confirmatory test for tin what colours are you looking for in a precipitate?

Yellowish or brownish

In the confirmatory test for nickel what colour are you looking for upon the addition of acid?

Red

In the confirmatory test for zinc what colour precipitate are you looking for?

White or white/greyish

In the confirmatory test for iron what colour of precipitate are you looking for upon the introduction of HCl, water and KSCN?

Dark red

In the confirmatory test for aluminium what colour precipitate are you looking for upon the adjustment of the pH to basic?

White

In the confirmatory test for chromium what colour are you looking for upon the addition of H₂O₂?

Dark blue

In the synthesis of Aspirin what are the objectives of the three phases?

Reaction: Synthesize aspirin from salicylic acid and acetic anhydride in the presence of a catalyst

Workup and purification: Isolate and purify it via cold water washes and recrystalization

Characterization: identify purity of Aspirin with infrared spectroscopy and NMR.

What are the three relevant functional groups in acetylsalicylic acid?

Carboxylic acid, Ester, Arene

Acetic anhydride reacts with water to form what product?

Acetic acid (C₂H₃OOH)

Write a balanced equation for the reaction between acetic anhydride with water.

C₄H₆O_{3 (aq)}+H₂O_(l)->2C₂H₄O_{2 (aq)}

Identify the functional groups of salicylic acid.

Carboxylic acid and alcohol

Why is it necessary to provide detailed structures of the reactants and products in the synthesis of aspirin and not just the molecular formulae for a balanced equation?

Because the chemical formulae can be configured into many different molecules, all with their own properties.

If synthesis of Aspirin failed what would you expect to see in the infrared spectroscopy and the NMR?

Failure would see a greater number of double bonds in salicylic acid than aspirin and there would be no esters present in the NMR as they are only present in aspirin but not any other reactants or products.

What is the catalyst in the synthesis of ASA?

H₃PO₄