Weak Acid-Strong Base Tiitration 2

Weak Acid-Strong Base Tiitration 2 - Weak Acid Strong Base...

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Weak Acid- Strong Base and Weak Base-Strong Acid Titrations Introduction The process of obtaining quantitative information of a sample using a fast chemical reaction by reacting with a certain volume of reactant whose concentration is known is called titration. The purpose of this experiment is just that, by titrating two acid bases we can find solution concentrations of two unknowns. In the first titration sodium hydroxide and acetic acid are the two strong base and weak acid used respectively. In the second titrations the strong hydrochloric acid and weak ammonia base shall be titrated. The two unknowns that are to be calculated are the sodium hydroxide and the hydrochloric acid. According to the Bronsted Lowry theory an acid is a molecule that has the ability to remove or get rid of a proton. The difference between a strong acid and a weak one is its ability to give protons away easily. Strong acid give protons away easily while weak acids do not. An base is a molecule that picks up protons. Each acid or base has a opposite conjugate acid and base, for example, if a strong acid gives protons away easily its corresponding base will be very weak vice versa for a base. Thus it can be said that acid base strength is dependent on the strength of the conjugate acid or base. These weak acids and bases all have specific ionization constants denoted as Ka or Kb. As for pH, this information is measured by calculating the concentration of hydronium ions in solution. The general equation is: pH = -log[H + ]. In this experiment pH shall be measured using an indicator known as phenolphthalein which changes color when solution reaches certain pH’s. But since this only measure pH certain levels, we use a more accurate tool, known as the pH meter. This pH meter which consists of a calomel electrode and a glass membrane electrode measures the electron motive force developed by the cell. The way the electrode reacts with the hydronium ion concentration is proportional, and the e.m.f built
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is fed through and is displayed digitally on the monitor. As mentioned before indicators shall be used, the two that are to be utilized are the phenolphthalein and methyl red will be used as indicators. Phenolphthalein changes to red from colorless within the pH range of 8.0 to 9.6. Methyl red changes from yellow to red within the pH range of 4.8 to 6.0. From the information attained, we shall be able to construct a pH curve which will tell us a number of things, such as the trend at which the titration takes place, the equivalence point, and regions of buffer, which when all combined will give us a good picture about the usefulness of titrations and the phenomenon of acid and base solutions. Procedure:
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Weak Acid-Strong Base Tiitration 2 - Weak Acid Strong Base...

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