Analytical Chemistry Laboratory: Measurements, Equilibrium, and Qualitative Analysis

A comprehensive set of flashcards designed to assist students in reviewing key concepts in analytical chemistry, focusing on measurements, equilibrium, and qualitative analysis.

What is the difference between an experimental value and the true value called?

Error.

How is accuracy defined in measurements?

The closeness of a measurement to the true or accepted value.

What formula represents Absolute Error (E)?

E = x - μ, where μ is the true value and x is the experimentally measured quantity.

What is Relative Error (%Er) formula?

%Er = (x - μ)/μ × 100.

What does precision measure in chemistry?

The closeness of results among themselves obtained in the same way.

What is the formula for Deviation (d)?

d = |xi - x̄|, where xi is an individual measurement and x̄ is the mean measurement.

How is Standard Deviation (s) calculated?

s = √(∑(xi - x̄)²/(N-1)), where N is the number of measurements.

What does Coefficient of Variation (CV) represent?

CV = (s / x̄) × 100.

What are Systematic Errors also known as?

Determinate Errors.

What are the causes of Systematic Errors?

Faulty instrument calibration, incorrect method, or human bias.

What type of errors affect accuracy?

Systematic (Determinate) Errors.

What are Random (Indeterminate) Errors?

Small, unpredictable changes during measurement.

What does TC stand for in glassware?

To Contain.

What types of glassware are classified as TC?

Volumetric Flask, Beaker, Erlenmeyer Flask.

What does TD stand for in glassware?

To Deliver.

What types of glassware are classified as TD?

Pipette, Burette, Graduated Cylinder.

What does molarity (M) represent?

Moles of solute per liter of solution.

What is the purpose of the dilution equation C1V1 = C2V2?

To relate initial and final concentrations and volumes during dilution.

What occurs to the concentration during dilution?

The concentration of the solution is reduced by adding more solvent.

What is phenolphthalein used for?

It is an indicator that turns pink in basic solutions.

What happens to the intensity of the pink color in a basic solution?

It is proportional to the concentration of hydroxide ions (OH−).

What are Primary Standards?

Highly pure, stable, non-hygroscopic compounds used to prepare solutions of known concentration.

What is an example of a Primary Standard?

Potassium hydrogen phthalate (KHP) (C8H5KO4).

What distinguishes Secondary Standards from Primary Standards?

Their concentration cannot be determined accurately by direct preparation alone.

What common issue do Secondary Standards often have?

They are often hygroscopic, volatile, or reactive with atmospheric components.

What is the process of determining the exact concentration of a secondary standard solution called?

Standardization.

What is titration?

A quantitative chemical analysis technique used to determine the concentration of a known reactant.

What does an endpoint in titration signify?

The point where a physical change occurs, indicating the reaction is complete.

What is Le Chatelier's Principle?

A principle stating that if a system at equilibrium is disturbed, the system will adjust to restore equilibrium.

What is a complex ion?

A metallic ion combined with other ions or molecules (ligands).

What role do ligands play in complex ion formation?

They bond with metallic ions to form complex ions.

What color does the cobalt aquo complex [Co(H2O)6]²⁺ exhibit?

Pink.

What happens when H2O is added to the cobalt complex equilibrium?

Equilibrium shifts to the left, favoring the pink color.

What effect does heating have on the cobalt complex equilibrium?

Equilibrium shifts to the right, favoring the blue color.

What is the main goal of qualitative analysis in a laboratory experiment?

To identify the various ions present in a sample.

How are cations separated in qualitative analysis?

By selective precipitation followed by confirmatory tests.

What group does the cation Ag+ belong to?

Group I Cations.

What is the group reagent for Group I cations?

6 M HCl.

What confirms the presence of Pb²⁺ in a solution?

A bright yellow precipitate of PbCrO4.

What solution is used to confirm the presence of Ag+ after ammonia treatment?

The supernatant containing [Ag(NH3)2]+ is treated with 6 M HNO3, which regenerates Ag+.

What solid confirms the presence of Hg2²⁺ during analysis?

The appearance of a gray solid.

What should be done with waste solutions containing hazardous ions?

Dispose of them in designated hazardous-waste containers.

What is the result when AgCl precipitate is re-acidified?

It will confirm the presence of Ag+.

What does the standard deviation tell you about data?

It measures the amount of variation or dispersion of a set of values.

What is the definition of concentration in a solution?

The amount of solute dissolved in a given amount of solvent.

What occurs during the dilution of a solution?

The amount of solute remains constant while the solvent amount increases.

What is the relationship between concentration and color intensity for phenolphthalein?

Darker pink indicates a higher concentration of basic hydroxide ions.

What is the function of an indicator in titration?

To signal the endpoint of the titration by changing color.

What is dynamic equilibrium?

A state where the rates of the forward and backward reactions are equal, with no net change.

Define the Law of Mass Action.

The rate of a reaction is proportional to the product of the concentrations of the reactants.

What does the equilibrium constant (Kc) express?

The ratio of the concentrations of products to reactants at equilibrium.

What effect does increasing temperature have in a system at equilibrium?

It can shift the equilibrium position to favor endothermic reactions.

How does cooling affect equilibrium in an exothermic reaction?

It shifts the equilibrium back towards the reactants.

What does a 6 M NH3 treatment lead to when separating Ag+ from Hg2²⁺?

AgCl dissolves to form a soluble complex, while Hg2Cl2 reacts to form a gray solid.

What is the purpose of rinsing glassware into waste containers?

To ensure proper disposal of hazardous materials.

What happens when phenolphthalein is present in acidic solutions?

It remains colorless.

What is the significance of accurately determining the concentration of a secondary standard?

It is essential for precise chemical analyses, like titrations.

Can the concentration of sodium hydroxide (NaOH) be determined directly by preparation?

No, it must be standardized against a primary standard.

What does the confirmatory test for Pb²⁺ involve?

Adding K2CrO4 to produce a yellow precipitate.

Which cation is separated from others by using hot water?

Pb²⁺.

What do chloride ions react with to form solid precipitates of mercury?

Hg2 2+.

What is the purpose of a confirmatory test in qualitative analysis?

To provide definitive evidence for the presence of specific ions.

What happens to the equilibrium when HCl is added to the cobalt complex?

It increases [Cl−], shifting the equilibrium to the right, favoring the blue complex.

What does the confirmatory test for Hg2²⁺ indicate?

The appearance of a gray solid.

What color does the chloro complex of cobalt exhibit?

Blue.

What does the term 'hygroscopic' refer to in relation to secondary standards?

The ability to absorb moisture from the air.

What precaution must be taken regarding sodium hydroxide (NaOH) solutions?

Store in PET containers to prevent CO2 absorption.

What happens to the equilibrium constant (Kc) if the temperature changes?

It may change, as Kc is dependent on temperature.

What is involved in the separation of cations during qualitative analysis?

Selective precipitation methods and confirmatory tests.

What measurement is crucial for determining the precision of a series of experimental results?

Standard Deviation.

What indicates that a titration has reached its endpoint?

A visible change such as a color shift due to the indicator.

What should be the primary steps in waste disposal for laboratory experiments?

Ensure hazardous waste is collected and properly disposed of in designated containers.

Which ions are pivotal to Group I cation analysis?

Ag+, Pb2+, Hg2 2+.

How does one confirm the presence of Ag+ after treating with NH3?

The formation of white AgCl precipitate upon re-acidification.

What factor is essential for maintaining the integrity of NaOH solutions?

Preventing exposure to air to avoid reaction with CO2.

What property of solutions makes PET containers suitable for storing NaOH?

Chemical resistance.

What is the mathematical relationship defined by the dilution equation during the dilution process?

C1V1 = C2V2.

What process involves adding solvent to reduce the concentration of a solution?

Dilution.

Identify the role of the indicator in acid-base titrations.

To indicate the endpoint of titration by color change.