The Ka expression, Ka=H+In-HIn [1] (1) is the equilibrium for the dissociation of the weak acid, where HIn is the acid and In- is the conjugate base. This is represented by the chemical equation: HIn ⇌H++ In- [1]Figure 1: Chemical equation for the dissociation of an acid-base indicator. Methyl red is a monoprotic organic acid. Figure 2 is a structural model of methyl red. Figure 2: Chemical structure of methyl red By plotting the data as the pH versus the log term of the Henderson-Hasselbach Equation, pH=pKa+logIn-HIn [2] (2) the pKa was
A pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH (acidity or basicity) of the solution can be determined visually. Hence a pH indicator is a chemical detector for hydronium ions (H3O+) or hydrogen ions (H+) in the Arrhenius model. Normally, the indicator causes the color of the solution to change depending on the pH. At 25° Celsius, considered the standard temperature, the pH value of a neutral solution is 7.0. Solutions with a pH value below 7.0 are considered acidic, whereas solutions with pH value above 7.0 are basic.
Phenolphthalein) is used to show the equivalence point has reached by changing colours. Titration experiments are used to determine the concentration of an acid or a base, if either acid or base concentration known, the other unknown concentration can be find out by measuring how much it takes to neutralize, which is a useful experiment. The Bronsted-Lawry theory about acid and base, describes as follows; an acid a proton (hydrogen ion) donor, a base is a proton (hydrogen ion) acceptor, or any component that can transfer proton to any other component is and acid and any component that accepts the proton is base. The theory says a substance can function as an acid only when a base is presented, and also other way round, a substance can only function as a base in the present of an acid. This theory consider a large
Reactivity: Caustic on organic matter Electric conductivity: Aqueous solutions or molten bases dissociate in ions and conduct electricity Common Bases Ammonia base is a weak base and can be found in window and floor cleaners. Brief Explanation of Experiment We have tested household substances to determine their pH level and description of pH(strong/weak, acid/base or neutral) Indicator An indicator is a substance that determines whether a substance is an acid/base/neutral. It changes the colour of the substance depending on how much water the substance contains. The pH measures the acidity in a solution. Prediction: Water: 7.0, Green, neutral.
CHE 131 Spring 2008 Experiment 4 - Determination of acetic acid in vinegar Preliminary Reading: Chang, 9th ed., section 4.7, pp. 150-153 Introduction: The principal component of vinegar (besides water) is acetic acid, HC2H3O2, a weak acid. In this experiment you will determine the concentration of acetic acid in a vinegar sample by titrating the acetic acid with the strong base sodium hydroxide, NaOH. The stoichiometry of the neutralization reaction is as follows: Molecular: Net Ionic: Neutralization: HC2H3O2(aq) + NaOH(aq) → NaC2H3O2(aq) + H2O HC2H3O2(aq) + OH¯ (aq) → C2H3O2+ (aq) + H2O H+(aq) + OH¯(aq) → H2O(aq) (1) (2) (3) Definition: The end point (also known as the equivalence point) of a titration occurs when the initial number of moles of H+ from the acid has been exactly neutralized by an equal number of moles of OH¯ ion from the sodium hydroxide: moles H+ = moles OH¯ (4) The only species present at the end point are the products, sodium acetate and water. For reasons that are beyond the scope of the material covered so far (but which will be covered in CHE 132), the solution is very slightly basic at the end point of a weak acid-strong base titration.
At this point the volume of base used to neutralized the acid can be determined. Phenolphthalein is the indicator which is colorless in an acid but changes to a faint and permanent pink color in base. The purpose of this experiment is to prepare a sample for titration with a base, become familiar with a buret while using proper titration technique in reaching an end point. Hypothesis : If I titrate a base of known concentration with an acid of unknown concentration then I can determine the concentration can be calculated because of the titration calculation. Materials : • Vinegar • Two small beakers (150mL) • 250-mL Erlenmeyer flask • 10-mL graduated cylinder • 50-mL buret • Buret clamp • Small funnel • M NaOH Hazards : • Chemical spill • Broken glass
Most differential stains have a challenge step that follows staining with a primary dye. In the Gram stain the challenge step is a rinse with either ethanol or acetone (either may be used). This step dehydrates and tightens the cell wall of Gram positives (mainly peptidoglycan) such that the rinse does not enter the cell. Gram negatives have mainly a lipid cell wall (even though they do contain peptidoglycan) that allows the challenge rinse to penetrate the cell and rinse out the crystal violet-iodine complex rendering the Gram negative cell colourless. Thus, the Gram negative cells must be stained to be seen, and this is done with the counter stain.
A wide choice of acid-base indicators is available, varying not only in the colours of the two forms but also in their sensitivity toward acid or base (Encyclopaedia Britannica, 2013). In relation to this practical the Sodium Hydroxide (NaOH) is the strong base which dissolves in water to form an alkaline solution. The concentration of this solution can be determined by titrating it with a standard solution of a strong acid such as Hydrochloric Acid (HCl). The indicator to be used is Methyl Orange. Apparatus: * * Pipette (10cm3) and Filler * Burette (50cm3) * Conical Flask * Funnel * Glass beaker * Stand and Clamp (for burette) * White paper * Chemicals (NaOH, HCl, Methyl Orange for indicator)
Maya Chamseddine 9m3 Mrs. Anwar science It might be said: Introduction: Indicators are used to test alkalinity and acidity of various items. These items may be present as either an acid chemical solution, basic chemical solution or a neutral chemical solution. Acidic solution meaning any item with a high PH, connoting potential hydrogen, neutral meaning nor a high or low PH and base meaning an item with a low PH. We use a PH scale to measure the concentration of acidity and alkalinity in a chemical solution. It is determined that acids tend to loose their potential hydrogen easily whereas bases are more than likely to hold on to their hydrogen.
Aim: | The aim of this experiment is to analyse a sample of vinegar and determine it’s concentration. | | | Hypothesis: | It’s expected that the aceatic acid will have the concentration of 0.1mol as this is the molarity of the NaOH as they have a 1:1 ratio of moles as it states in their chemical equations. | | | Apparatus: | * 1 x retort stand * 1 x retort burette clamp * 1 x burette * 1 x pipette * 1 x glass funnel * 2 x Conical Flasks * Sheet of filter paper * 200mL of 0.1 mol L-1 NaOH * 200mL of acetic acid of unknown concentration | | | Procedure: | 1. WARNING: Wear safety glasses and gloves! 2.