LAB (QUIZ 1): GRAVIMETRIC & TITRATION Flashcards
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Define
Gravimetric analysis
Gravimetric analysis measures the amount of a substance by separating it from a sample and weighing the isolated component.
Gravimetric analysis is a quantitative method for accurately determining the amount of a substance by selective precipitation of the substance from an aqueous solution. The precipitate is separated from the remaining aqueous solution by filtration and is then weighed. Assuming that the chemical formula for the precipitate is known and that the precipitation reaction goes all the way to completion, then the mass of the substance in the original sample can be determined.
Enumerate
What are the 8 steps in Gravimetric Analysis
- Preparation of the solution
- Precipitation
- Digestion
- Filtration
- Washing
- Drying/Igniting
- Weighing
- Calculation
Identify
What is the title of the experiment 1?
Gravimetric determination of Sulfate Ions in a water sample via sulfate precipitation
Enumerate
What are the objectives of the experiment?
- To experimentally analyze an unknown sulfate salt via a precipitation reaction, using the techniques associated with
Gravimetric Analysis to collect and weigh the precipitate, and - To calculate the percentage by mass of SO4 in the unknown sulfate salt via a stoichiometric analysis of the collected precipitate, and then use this percentage to identify the metal “M” present in the sulfate salt.
What is titration?
Titration is the slow addition of one solution of a known concentration (called a titrant) to a known volume of another solution of unknown concentration until the reaction reaches neutralization, which is often indicated by a color change.
The solution called the ____ must satisfy the necessary requirements to be a primary or secondary standard.
titrant
Draw the schematic diagram for Experiment 1.
1. Mixture of H2SO4 + 200 mL H2O
* add 4 mL HCl
* Heat until boiling
2. Mixture of sulfate water + 30 mL BaCl2
* Stir vigorously while heating
3. Filter
* Add drops of BaCl2
* filtrate
* add small amount in a 5 mL test tube
* chloride test (adding few drops of AgNO3)
* Clear solution: collect precipitate
4. Precipitate
* place in pre-weighed petri dish
* dry in oven at 110 degrees celsius
* weigh
What is Acid-Base titrations?
Acid-Base titrations are usually used to find the amount of a known acidic or basic substance through acid base reactions.
Draw the set-up for Experiment 2
see google
What is a titrant? In our experiment what was the tirant?
Titrant is a solution of a known concentration, which is added to another solution whose concentration has to be determined.
In our experiment sodium hydroxide was the titrant.
What is a titrand? In our experiment what was the tirand?
Titrand is the solution whose concentration has to be determined.
In our experiment the acetic acid in the vinegar sample is the titrand.
Chemical equation for Experiment 2.
NaOH (aq) + HC2H3O2 (aq) → NaC2H3O2 (aq) + H2O (l)
Chemical equation for Experiment 1
Ba (aq) + SO4 (s) → BaSO4
SO4 + BaCl2 → BaSO4 + 2Cl
Draw the schematic diagram for Experiment 2.
1. Weigh ___NaOH to prepare 0.1 M NaOH (2000 mL)
2. Weigh 1.0211 g KHP
* dissolve in 50 mL water
* use 10 mL aliquots to standardize NaOH
* Add 1 drop of 1% phenolphthalein to 10 mL
* transfer NaOH in a burette
* titrate
3. Prepare 10 mL vinegar
* add 0.25% phenolphthalein
* titrate with NaOH until color changes to pale pink
What is an equivalence point?
The equivalence point is the point in a titration where the amount of titrant added is enough to completely neutralize the analyte solution.
What is an end point?
The point at which the indicator changes color is called the endpoint.
What is the purpose of an indicator?
the addition of an indicator to the analyte solution helps us to visually spot the equivalence point in an acid-base titration.
