Phenolphthalein Lab Report

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Phenolphthalein is often used as an indicator in acid base reactions. The reaction used in this lab is:
C_20 H_14 O_(4 (aq))+46 NaOH_((aq))→46 Na_( (aq))^++20 H_2 CO_(2 (aq))+10 H_2 O_((l)).
Phenolphthalein and sodium hydroxide react to form carbonous acid, water, and Na+ ions. This reaction is a neutralization reaction, where phenolphthalein, a weak acid, reacts with a strong base, sodium hydroxide. When phenolphthalein is put into a basic solution, it turns pink. The phenolphthalein ion is pink, and when a base and phenolphthalein are combined, more H+ ions are removed and the equilibrium moves to the right. At the endpoint of a reaction, all of the H+ ions have reacted and been neutralized, so the phenolphthalein ionizes resulting in a
…show more content…
For both trials, we used 25ml of Sprite. In Trial 1, 5.3ml of sodium hydroxide was added to the solution via titration. In Trial 2, 5.2ml of sodium hydroxide was used. To calculate molarity for Trial 1, we used the molarity of sodium hydroxide (NaOH), .101 and multiplied this number by the milliliters of NaOH used, 5.3. Then we used the molar relationship from the equation and divided by 3 moles of NaOH which is related to 1 mole of Acid, because they have a 3:1 relationship respectively. Finally, we divided by the militers of soda used, which was 25. This resulted in a molarity of .007M. For Trial 2, the process is the same except we multiply by 5.2ml of NaOH used instead of 5.3ml. These calculations still produce a molarity of .007M. This means that the average molarity of citric acid in the sample is .007M. We use this determined molarity to find the moles of citric acid per bottle of Sprite and the mass of citric acid per bottle of soda. The bottle of soda we used was a 2 liter bottle, which means the volume of the container of soda is 2 liters or 2000 milliliters. So, to find the moles of citric acid per bottle of soda, we multiplied the average value of molarity of citric acid in the sample, which is .007, by 2 liters because molarity is in moles per liter and we have a 2 liter container of soda. Through this multiplication it is determined that there are .014 moles of citric acid per bottle of Sprite. Then from the number of moles of citric acid per bottle of soda, the mass of citric acid per bottle of sprite can be calculated. If you multiply the number of moles of citric acid per bottle of soda, 0.14 moles, by the molecular weight of citric acid, 192.12g/mole, the mass of citric acid per bottle of soda is found. The mass of citric acid per 2 liter bottle of Sprite is 2.69 grams. There is less citric acid in a 2 liter bottle of Sprite than a 2 liter bottle of Sierra

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