Experiment: Determining pH of identical strong and weak solutions Date: 31/10/03 Aim: Plan and perform a first-hand investigation to measure the pH of identical concentrations of strong and weak acids. Equipment: Deionised water (H2O) Tartaric Acid (C4H6O6) Citric Acid (C6H8O7) Sulfuric Acid (H2SO4) Acetic Acid (CH3COOH) Hydrochloric Acid (HCl) Ammonium Chloride (NH4Cl) tap water (H2O) Nitric Acid (HNO3) Probe Ferric chloride (FeCl3) Wash bottle Sodium Chloride in tap water (NaCl) Beakers Sodium Chloride in deionised water (NaCl) data logger Method: 1) Make sure there is an equal molarity of each substance. In this case 0.1 moles/litre. Therefore there are 0.1 moles of each substance in solution. 2) Place each of the substances in a beaker. 3) Calibrate the data logger by using buffer zones of pH 4 and 10.
4) Place the probe into one beaker and click the start button on the data logger. Record the pH level of the substance. 5) Remove the probe and wash thoroughly using the wash bottle. 6) Repeat for all the other substances and record their pHs. 7) Determine which solutions are strong and which are weak. Results: Substance pH Acidic, Basic or Neutral Strong or Weak Citric Acid (C6H8O7) 2.4 Acidic Weak Acetic Acid (CH3COOH) 3.0 Acidic Weak Tartaric Acid (C4H6O6) 2.3 Acidic Weak Nitric Acid (HNO3) 1.5 Acidic Strong Hydrochloric Acid (HCl) 1.5 Acidic Strong Sulfuric Acid (H2SO4) 1.4 Acidic Strong Ferric chloride (FeCl3) 1.5 Acidic Strong Ammonium Chloride (NH4Cl) 7.0 Neutral – Sodium Chloride in deionised water (NaCl) 5.6 Acidic Very Weak Sodium Chloride in tap water (NaCl) 7.2 Neutral – Deionised water (H2O) 6.0 Neutral – Tap Water (H2O) 7.0 Neutral – Discussion: By observing our results it can be seen that even though all solutions have the same concentration they can still be strong or week. It can be seen that all organic acids eg.
The Element: Chlorine General Information We researched the chemical element known as chlorine. Chlorine hasan atomic number of 17 and an atomic weight of 35. 453. It has a valence number of 3. The element has 3 energy levels. Chlorine exists as a greenish-yellow gas at normal temperatures and pressures. Chlorine is second in reactivity only to fluorine among the halogen elements. Chlorine is a ...
Acetic acid, Citric acid and Tartaric acid are all weak acids whereas all inorganic acids such as Sulfuric acid, Nitric acid and Hydrochloric acids were strong. It was also discovered that ionic molecules could be acidic eg. Ferric Chloride. In the past it has been said that all ionic substances tend to be more neutral than acidic or basic. This has all been changed now and we have the Brnsted Lowry concept. With the Brnsted-Lowry concept we usually refer to a hydrogen ion as a proton.
That is because a proton is all that is left when a hydrogen atom loses an electron to become an ion. Brnsted and Lowry independently came up with the idea that an acid is an acid because it provides or donates a proton to something else. When an acid reacts, the proton is transferred from one chemical to another. Note that in order for an acid to act like an acid, there needs to be something for it to react with. There needs to be something to take the proton. There needs to be a base. A base is a proton acceptor. Compare this to the definition that an acid is a proton donor.
Bases are the opposite of acids. Bases are basic because they take or accept protons. Hydroxide ion, for example can accept a proton to form water. Brnsted and Lowry realized that not all bases had to have a hydroxide ion. As long as something can accept a proton it is a base. So anything, hydroxide or not, that can accept a proton is a base under the Brnsted-Lowry definition.
Example: HCl (aq) + H2O (l) H3O+ (aq) + Cl – (aq) [strong acid] And CH3COOH (aq) + H2O (l) H3O+ (aq)+ CH3COO (aq) [weak acid] Citric Acid: A water-soluble weak organic tribasic acid found in many fruits, esp. citrus fruits, and used in pharmaceuticals and as a flavouring (E330).
Acids and Bases are two groups of chemical compounds that generally have opposite characteristics. They have there own unique traits, acids taste sour, turn litmus red while bases taste bitter and turn litmus blue. The term pH relates to measuring the acidity or alkalinity of a solution, such as vinegar, or even a damp substance like soul. The neutral pH is 7, which is essentially water, with ...
It is extracted from citrus fruits or made by fermenting molasses and is an intermediate in carbohydrate metabolism. Tartaric Acid: Dihydroxysuccinic acid; made from crude tartar; a laxative and refrigerant; used in the manufacture of various effervescing powders, tablets, and granules. The main disadvantage of this experiment was that the probe had to be washed thoroughly after each substance was tested or else some residue might be left behind altering the pH of the next substance. Also it was necessary to keep the electrical items used in the experiment away from the solutions so nothing is spilt onto the electrical items.
Risk Assessment: Care must be taken when handling the substances, as some can be harmful. Especially those substances with a low pH level, because if spilt on the skin, irritation may occur or burning. Conclusion: The pH of identical strong and weak substances was determined by performing a first-hand investigation..