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Acid Concentration Deconstruction Practical - Coggle Diagram
Acid Concentration Deconstruction Practical
Acids
What is an Acid?
Acidic substances have a pH value below 7. pH is an inverse logarithmic scale correlating to the relative amount of free hydrogen ions present. Acidic substances have greater hydrogen ions.
Examples of Acids
Household Acidic Substances
Lemon Juice:
Lemon juice was chosen due to its high availability and moderate acidity due to an unknown concentration of citric acid. Since it is a food product, the result can be compared to food safety standards.
Rust remover E.g. CLR:
Very acidic, however contains multiple types of acids which increase the complexity of calculations.
Battery Acid:
Difficult to obtain and has a pH of 0, highly acidic and extremely dangerous.
Vinegar
Soft Drinks:
Carbonation decreases the accuracy of volume measurements.
Baking Soda
Pool Cleaner
Hair Dye
Sulfuric Acid
Hydrochloric Acid
Citric Acid
Nitric Acid
Acetic Acid
Carbonic Acid
Measuring concentration
In chemistry, concentration is the measure of a solute present generally measured in moles or grams, in a volume of solvent.
Titration:
A solution of unknown concentration is reacted with one of a known concentration. The quantity of solution required to react all present substance is known as the titre value and can be used to calculate concentration. An acid-base titration can be used to find the concentration of an acid.
Evaporation:
A solution is heated until the solvent, usually water is evaporated. The remaining solute can be measured to determine the concentration. Does not separate solutes therefore impractical in solutions containing multiple compounds.
Absorbance:
Light of specifc have lengths is passed through a solution. The amount of light absorbed is measured. Using the collected data, the concentration of the solution can be calculated using Beer Lambert's Law.
Titration
Method
Preparing Standard Basic Sodium Carbonate Solution:
Measure 1.2 g of sodium carbonate and place in volumetric flask. Fill the flask with distilled water up to 200 mL calibration line and swirl to dissolve.
Conducting Titration:
The basic sodium carbonate is placed in the conical flask with pH indicator and the acidic lemon juice in the burette. Substances combined to react gradually until pH is neutral, the is the end point, thus titre value used for calculations.
Equivalence Point:
When the two reactants have reacted entirely reacted in the correct ratio.
End Point:
When the pH of the created solution goes past neutral and goes between acidic and basic.
Concordant Values:
Titre values that are within one decimal place of each other. When three are obtained, their average is taken for calculations.
Materials
Basic Solution
Sodium Carbonate:
Sodium Carbonate is highly basic substance that will create with citric acid to create a neutral solution of sodium citrate, water and some carbon dioxide gas.
Sodium Hydroxide
Potassium Hydroxide
pH Indicator
Methyl Orange:
Methyl orange transitions from pale yellow to a dark orange colour when the solution goes from basic to acidic, thus is ideal for this base to acid titration.
Universal Indicator:
Universal indicator contains a variety of chemicals which produce a gradient of colour changes depending in the pH of a substance. Since it is a gradient, it is not ideal for a titration.
Phenolphthalein
Bromothymol Blue
Phenol Red
Acidic Solution
Lemon Juice Drink
Apparatus
50 mL Burette
20 mL Volumetric Pipette and Filler
Teat Pipette
250 mL Volumetric Flask
Retort Stand
250 mL Conical Flask
Clamp
White Ceramic Tile
Weighing Scale
Watch Glass
Funnel
Stoppper
Expected Results:
Generally, lemon juice drink will has a citric acid concentration between 1.014 and 7.439 g/L. It is expected the result will lie within these bounds.
Practical Write Up
Variables
Uncontrolled
Temperature
Air pressure
The rate at which basic solution is added
Controlled
Type of basic solution:
Different substances will react differently and in different ratios.
Volume of basic solution:
Changes number of moles of basic substance present.
Concentration of basic solution:
Changes the amount of substance present for a given volume of solution.
Type of indicator used:
Different indicated change colour at different pH levels.
Risk Assessment
Glassware:
Shattered glass poses a risk of very dangerous glass cuts.
Working with chemicals:
Chemical burns can be caused by highly acidic and basic substances
General laboratory risks:
In a lab, there are many substances and equipment that may pose a risk.
Calculations
Stoichometry
Errors
Determining the end point of the reaction since colour change judged by eye.
Measurement errors. Equipment calibrations and human error
Contaminating substances