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Questions and Answers
Questions and Answers
In a titration experiment, what is the purpose of standardizing a NaOH solution?
In a titration experiment, what is the purpose of standardizing a NaOH solution?
- To introduce impurities into the NaOH solution.
- To evaporate excess water from the NaOH solution.
- To decrease the concentration of the NaOH solution.
- To accurately determine the molarity of the NaOH solution. (correct)
Why is distilled water used to rinse an Erlenmeyer flask in the procedure for standardizing an acid solution by titration?
Why is distilled water used to rinse an Erlenmeyer flask in the procedure for standardizing an acid solution by titration?
- To increase the volume of the acid being titrated.
- To introduce additional ions into the solution to enhance conductivity.
- To heat the flask and speed up the reaction.
- To remove any potential contaminants that might affect the titration's accuracy. (correct)
In complexometric titration for water hardness, what is the role of EDTA?
In complexometric titration for water hardness, what is the role of EDTA?
- To oxidize organic matter present in the water.
- To bind to metal ions, allowing for determination of water hardness. (correct)
- To reduce the pH of the water sample.
- To precipitate metal ions in the water sample.
Why is Eriochrome Black T used as an indicator in EDTA titrations for water hardness?
Why is Eriochrome Black T used as an indicator in EDTA titrations for water hardness?
What potential problem would result from inadequate silver ions in the gravimetric analysis of chloride?
What potential problem would result from inadequate silver ions in the gravimetric analysis of chloride?
Why are porcelain crucibles heated and cooled in a desiccator during gravimetric analysis of chloride?
Why are porcelain crucibles heated and cooled in a desiccator during gravimetric analysis of chloride?
How is the equilibrium of the reaction $HCl + H_2O \rightleftharpoons H_3O^+ + Cl^-$ affected by the relative strengths of the acids and bases involved?
How is the equilibrium of the reaction $HCl + H_2O \rightleftharpoons H_3O^+ + Cl^-$ affected by the relative strengths of the acids and bases involved?
Why is it essential to use distilled or deionized water when washing the electrode of a pH meter between measurements?
Why is it essential to use distilled or deionized water when washing the electrode of a pH meter between measurements?
What is the significance of using a large volume of water when determining the enthalpy of solution for a substance?
What is the significance of using a large volume of water when determining the enthalpy of solution for a substance?
In determining the enthalpy of combustion of ethanol using a simple calorimeter, what is the purpose of stirring the water while heating?
In determining the enthalpy of combustion of ethanol using a simple calorimeter, what is the purpose of stirring the water while heating?
In the reaction of cyclohexane with bromine water, what condition favors the substitution reaction and formation of hydrogen bromide?
In the reaction of cyclohexane with bromine water, what condition favors the substitution reaction and formation of hydrogen bromide?
How does Baeyer's test distinguish between alkanes and alkenes?
How does Baeyer's test distinguish between alkanes and alkenes?
What structural feature distinguishes alcohols from phenols?
What structural feature distinguishes alcohols from phenols?
What dictates the differing reaction rates of primary, secondary, and tertiary alcohols with the Lucas reagent?
What dictates the differing reaction rates of primary, secondary, and tertiary alcohols with the Lucas reagent?
Why does the ester methyl salicylate have a warming sensation, which is odd, when applied topically?
Why does the ester methyl salicylate have a warming sensation, which is odd, when applied topically?
During the gravimetric analysis of chloride, which step ensures that the precipitated silver chloride is pure and free from contaminants?
During the gravimetric analysis of chloride, which step ensures that the precipitated silver chloride is pure and free from contaminants?
What factor determines if water hardness is classified as temporary?
What factor determines if water hardness is classified as temporary?
In a lab, what should be done immediately if a chemical splashes into your eyes?
In a lab, what should be done immediately if a chemical splashes into your eyes?
What type of glassware should never be heated directly with an open flame and must only be heated using a heating mantle or water bath?
What type of glassware should never be heated directly with an open flame and must only be heated using a heating mantle or water bath?
You accidentally spill a concentrated acid on the benchtop. What is the most appropriate first action?
You accidentally spill a concentrated acid on the benchtop. What is the most appropriate first action?
Why should acids always be added to water slowly, rather than adding water to acid?
Why should acids always be added to water slowly, rather than adding water to acid?
What is the primary reason safety goggles should be worn at all times in the lab?
What is the primary reason safety goggles should be worn at all times in the lab?
Given solutions of $HCl$, $CH_3COOH$, $NaCH_3COO$, $H_2CO_3$, $NaHCO_3$, $NH_3$, and $NaOH$, how would you appropriately measure the pH for each solution?
Given solutions of $HCl$, $CH_3COOH$, $NaCH_3COO$, $H_2CO_3$, $NaHCO_3$, $NH_3$, and $NaOH$, how would you appropriately measure the pH for each solution?
What are the signs of a good quality lab report?
What are the signs of a good quality lab report?
What is the primary reason for using a pipette bulb instead of mouth-pipetting in a chemistry lab?
What is the primary reason for using a pipette bulb instead of mouth-pipetting in a chemistry lab?
Suppose a procedure calls for using $250 ,\text{mL}$ of a $0.1 ,\text{M}$ $NaCl$ solution, but instead suggests 'A $250 ,\text{mL}$ solution of $0.01 ,\text{M}$ $NaCl$ was prepared’. What is the reason for this kind of language
Suppose a procedure calls for using $250 ,\text{mL}$ of a $0.1 ,\text{M}$ $NaCl$ solution, but instead suggests 'A $250 ,\text{mL}$ solution of $0.01 ,\text{M}$ $NaCl$ was prepared’. What is the reason for this kind of language
What is the purpose of using concentrated sulfuric acid in esterification reactions?
What is the purpose of using concentrated sulfuric acid in esterification reactions?
What is one of the functional requirements to be a multidentate ligand?
What is one of the functional requirements to be a multidentate ligand?
What causes soap scum when using hard water?
What causes soap scum when using hard water?
What is the purpose of using a desiccator after high temperature exposure, such as drying something in the oven?
What is the purpose of using a desiccator after high temperature exposure, such as drying something in the oven?
If a water source has a high concentration of $\text{Mg}^{2+}$ and $\text{Fe}^{3+}$, how would it be classified?
If a water source has a high concentration of $\text{Mg}^{2+}$ and $\text{Fe}^{3+}$, how would it be classified?
According to the context, which of the following compounds will be considered as base?
According to the context, which of the following compounds will be considered as base?
When preparing to add hydrochloric acid ($HCl$) to a beaker of water, it is essential to ensure what?
When preparing to add hydrochloric acid ($HCl$) to a beaker of water, it is essential to ensure what?
What is the first step a gravimetric operator should take before starting the procedure?
What is the first step a gravimetric operator should take before starting the procedure?
Questions and Answers
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Flashcards
Flashcards
Lab safety rule
Lab safety rule
Protective eyewear is mandatory in the lab at all times.
Contact lenses in lab?
Contact lenses in lab?
Avoid wearing them in the lab due to potential chemical absorption.
Lab shoes
Lab shoes
Essential for safety to prevent injuries from dropped items.
Hair and clothing
Hair and clothing
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Lab coat
Lab coat
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Handling chemicals
Handling chemicals
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Experiments
Experiments
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Eating and drinking
Eating and drinking
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Pipetting
Pipetting
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Chemical touch
Chemical touch
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Chemical skin contact
Chemical skin contact
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Chemical disposal
Chemical disposal
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Safety data sheets
Safety data sheets
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Working alone
Working alone
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Emergency procedures
Emergency procedures
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Report accidents
Report accidents
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Clothing fire
Clothing fire
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Extinguishers
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Chemical in eyes
Chemical in eyes
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Chemical spills
Chemical spills
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Eyewash
Eyewash
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Injuries
Injuries
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Personal responsibility
Personal responsibility
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Smelling vapors
Smelling vapors
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Mixing acid and water
Mixing acid and water
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Glass stoppers
Glass stoppers
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Measurements in Chemistry
Measurements in Chemistry
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Pipette calibration
Pipette calibration
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Acid-base titration
Acid-base titration
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Water Hardness
Water Hardness
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Gravimetric analysis
Gravimetric analysis
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Acids and bases
Acids and bases
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pH Buffers
pH Buffers
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Enthalpy of Solution
Enthalpy of Solution
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Enthalpy of Combustion
Enthalpy of Combustion
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Study Notes
Study Notes
- Chemistry Laboratory RP 273 Lab Manual was compiled by Ami Johannes in November 2021
Laboratory Safety Rules
- Lab safety rules are based on common sense, emphasizing awareness of surroundings
- Wear eye protection (goggles or approved glasses) at all times, avoiding contact lenses
- Wear closed-toe shoes to protect against dropped glassware
- Confine long hair and loose clothing; use a lab coat
- Use correct apparel when handling dangerous chemicals like a lab coat, apron, gloves and face shield
- Perform only authorized experiments with specified chemicals and quantities
- No eating or drinking is allowed in the lab
- Never use mouth-pipetting, and always instead use a pipette bulb
- Avoid touching chemicals, as many are absorbed through the skin
- Wash off skin chemicals with ample water
- Dispose of chemicals in designated collection bottles, not the sink, after consulting the TA
- Small quantities of innocuous reagents may be flushed down the sink with running water after consulting the TA
- Learn chemical hazards from material safety data sheets
- Never work alone; ensure at least one other person is present, with the instructor or TA available
Emergency Procedures
- Read posted emergency directions and in emergencies, notify occupants, evacuate, and call 911
- Immediately report fires or accidents to the instructor or TA
- Do not run if clothing catches fire; use the fire blanket or emergency shower to extinguish flames
- Know where fire extinguishers and eyewash stations are located
- Flush eyes with water for 15 minutes if exposed to chemicals and seek immediate medical attention
- Wash chemical spills on the body or clothing with large amounts of water, using the emergency shower, and remove affected clothing
- Know the location of the emergency shower and eyewash sink
- Report all injuries to the instructor or TA
Lab Report Guidelines
- Lab reports should be a typewritten, lengthier version of the lab notebook in paragraph form without an outline
- A lab report should have a title page (5 points) with the experiment title, experiment names, and experiment dates
- An introduction or background section (20 points) explains the experiment's purpose, analysis, methods, theory, and pertinent chemical equations
- The procedure section (15 points) summarizes the experiment's steps in past tense, including instrumental parameters and relevant references
- The data section (30 points) presents tabulated data with titles/numbers and includes appropriate figures with titles, numbers, and sample calculations
- The results and discussions section (25 points) discusses results, trends, findings, objectives, error sources, and improvement suggestions
- A references section (5 points) lists author, title, edition, city, publisher, and publication year
- Write-ups must use the past progressive tense and avoid pronouns like "I" or "We"; for example, "A 250 mL solution of 0.01 M NaCl was prepared"
Experiment 1: Pipette Calibration
- The experiment determines the accuracy of a pipette
- Uncertainty exists in chemistry lab measurements, so it should be minimized for precision and accuracy
- Calibrating ensures pipette accuracy
- Pipette accuracy is determined using D=M/V
- Determine pipettes volume using the equation, distilled water mass, and waters density
- An analytical scale and list of waters densities at various temperatures determines volume to four digits
- Repeat measurement indicates precision.
Pipette Calibration Materials
- Pipette
- Pipette bulb
- Analytical balance
- Kim wipes (tissue paper)
- Vial, small Beaker, or flask
- Unknown liquid
Pipette Calibration Safety
- Wear safety goggles and an apron in the lab
- Never use mouth suction for a pipette: only a pipette bulb
- Treat balances carefully as they are very delicate
Pipette Calibration Procedures:
- Accurately weigh a small, clean flask/beaker; record that mass
- Fill the pipette carefully, adjust the water to the line, and transfer its contents
- Weigh the container with water, and record the value
- Repeat the procedure four more times
- Measure water temperature, and find water density in a table and record the density
- Calculate the pipette volume using the water mass and density and then calculate the average volume and SD of measurements
- Calculate % relative error in the 10 mL pipette specification
- Determine determination precision for pipette volume and express as a relative SD in parts per thousand
Experiment 2: Acid-Base Titration
- The purpose of this lab is to experimentally determine the concentration of an unknown base solution
- The experiment is in four parts:
- Preparation of NaOH solution of unknown base and it's standardization and titration for an acids exact concentration
- With the acid solution from Part 3, experimentally determine the unknown base concentration
Experiment 3: Water Hardness
- Hard water occurs due to dissolved metal ions (minerals like Ca2+, Mg2+, Fe3+, SO42, HCO3) in groundwater
- Water hardness is measured with CaCO3.
- Measuring water hardness determines water quality for home and industrial use
- Originally, water hardness measured the capacity of water to precipitate soap
- Hard water is not a health hazard, but contributes calcium and magnesium to human diet
- Hard water causes soap scum as calcium ions bind to soap
- Heated water precipitates CaCO3 causing damage and malfunction
- Water softeners remove hardness, replacing Ca2+ with Na+ which makes it too salty for drinking
Types of Water Hardness:
- Temporary hardness is when bicarbonate ion, HCO3 is present in the water, removed by boiling: HCO3 <-> H2O + CO2(g)
- Permanent hardness happens when ions Ca2+, Mg2+, Fe3+, and SO42 are in water and cannot be eliminated by boiling
Water Hardness Degrees:
- Soft Water has CaCO3 concentration is 0 - 75 mg/L
- Medium hard Water has CaCO3 concentration is 70 - 150 mg/L
- Hard Water has CaCO3 concentration is 150 to 300 mg/L
- Very hard Water has CaCO3 concentration > 300 mg/L
- Permanent hardness is found by titrating in a stndard solution using ethylenediamminetetra acetic acid, EDTA
- EDTA is a chelating agent used to capture metal ions, softening the water by binding tightly to the metal ions
- EDTA is a versatile chelating agent, which molecules can form multiple bonds to a single metal ion
- Chelating agents are multi-dentate ligands; ligands are substances that bind metal ions
- Multidentate ligands are many clawed, and hold firmly to metal ions for stable complex
EDTA Uses
- EDTA forms complexes with calcium and magnesium ions, and is used in soaps and detergents
- EDTA is used for hard water, to remove ions from the enzymes that spoil food and to promote the color retention foods
- The lab determines total permanent hardness
- EDTA binds all metal ions (not just Ca2+), resulting in a 1% experimental error
EDTA Endpoint Color Change:
- Eriochrome Black T indicator is used in the titration
- The chelated or acidified form is PINK RED while the non-chelated basic form is BLUE
Experiment 4: Gravimetric Analysis
- Gravimetric analysis isolates a desired constituent in pure/combined form, weighs the isolated constituent, and then the percentage of the constituents is calculated,
- Precipitation affects inorganic/organic precipitating agents
Inorganic Precipitation agents
- Silver nitrate is an inorganic precipitation agent, precipitates halide ions like chloride
- Barium chloride precipitates sulfate ion.
- Potassium, rubidium, cesium ions are precipitations with sodium tetraphenylborate
- The product is a salt since it reactions occur between ion and anions, bonding is electrovalent
- Organic reagents contain carboxyl and hydroxyl groups, ionize into anions, and combine with cations to create insoluble salts (bonding is electrovalent here)
- Silver ions undertake a reaction with chloride
- Silver chloride relatively insoluable compound, solubility product Ksp = [Ag+] [Cl]) of 1.8 10-10.
Experiment 5: pH And Buffer Solutions
- Acids donate protons (hydrogen ions), while bases accept protons based on the Bronsted-Lowry theory
- Acids donate protons while bases accept them
- Strong acids/bases and weak acids/bases have varied strengths
Experiment 6: Enthalpy of Solution (ΔHs)
- One mole of a substance is dissolved in water and the temperature change is recorded, but no more heat is added
Experiment 7: Reaction Of Hydrocarbons
- Hydrocarbons are classified in a few types that differ based off sturcture like:
- Alkanes have single bonds (saturated)
- Alkenes and Alkynes have double/triple bonds (unsaturated)
- Aromatic hydrocarbons are cyclic (benzene-related)
- This experiment explores fundamental reactions of saturated, unsaturated, and aromatic hydrocarbons (reacting differently with reagents)
Experiment 8: Identification Of Alcohols And Phenols
- Specific atoms determine an organic m molecule's properties
- These groups are called functional groups, like the hydroxyl in alcohol
- Alcohols are used frequently in solvents, drugs and disinfectants
9: Synthesis of Esters
- A class of organic compounds prepared from the reaction of a classification reaction of an organic acid with alcohol with a strong acid (H2SO4)
- They impart aromas associated with the different fruits used in cosmetics and perumes
- Esters posses important psychological effets like acetylsalicyclic (aspirin) acts as an analgesic and an antipyretic
Liniments:
- Liniments contain methyl salicylate, which is prepared from reacting methyl alcohol with thesalicylic acid group.
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