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Objectives of the experiment
These varied ranges of experiment are aimed at determining the quantity of moles counterbalanced by a marketable antacid tablet.
Antacids are made and sold for the purpose of counteracting acid congestion in our stomach. Symptoms such as heartburns are because of too much acid, which, for the sake of this evaluation can be comfortable assumed to be only hydrochloric acid. Antacids such as sodium hydroxide and aluminum hydroxide either act as a buffer solution or counterbalance the acid in the stomach. The commonly used antacids as approved by Food and Drug administration include hydrogen carbonates, metallic hydroxides, and metallic carbonates (Bailey 1996; Singh 2009).
A simple and effective way of analyzing antacid preparations is by establishing the number or amount of moles of hydrochloric acid will be counterbalanced by well-known weight of antacid(Bailey, 1996). This is easily achievable by using back titration technique where a technician "adds more of standardized hydrochloric acid solution to the antacid tablet than the tablet can be neutralized and then titrate unneutralized hydrochloric acid with standardized NaOH" (Bailey, 1996, p. 4).
Weigh each antacid tablet and mix with 40 mL of 0.1 M HCl in separate Erlenmeyer flask. Add 0.05 M NaOH drop-by-drop to back-titrate the solution until the pH is neutral. Record the volumes and do calculations.
Results and Discussion
In this experiment, Maalox Tums Mylanta CVS brand Rennies, the following mL of sodium hydroxide was used: 20.0 g 24.1, 21.0 g 22.4 mL, 18.0 g 20.0 mL, 18.3 g 19.9 mL, and 7.5 g 24.4 mL.
1. a)Taking 20.0g 24.1ml of NaOH used in neutralization we have balanced equation as: OH-(aq) + H30+ (aq) 2H20(l)
From standardized NaOH From excess HCl
From the equation, 1mol of HCl is counterbalanced by 1mol of NaOH. Taking A= initial number of moles of HCl added to a tablet, B=number of moles of NaOH needed for back-titration and N=the number of moles of HCl counterbalanced by a tablet. We express the equation as N=A-B. The number of moles of HCl added to tablet (A) = (VHCl) (MHCl). Therefore A=0.04L x 0.1 M HCL=0.004mole of HCl added to tablet. We also find the number of NaOH used in back-titration (B) = (VNaOH) (MNaOH). Molarity of NaOH is given by= (20.0/40) x (1000/24.1)=20.7M. Therefore moles of NaOH used=20.7M x24.1/1000= 0.4989 moles of NaOH (B) used. We know that the number of sodium hydroxide required equals the quantity of moles of excess hydrochloric acid hence HCl in excess was 0.4989moles.
b) For 21.0 g, 22.4 mL .Molarity of NaOH = (21.0gX1000)/22.4mLx40=23.44M. Therefore moles of NaOH used=23.44X22.4/1000=0.5251moles to neutralize excess acid.
c) 18.0 g, 20.0 mL. Molarity of NaOH=(18.0gx1000)/20.0mLx40=22.5M. Hence moles of NaOH used= 22.5X20/1000=0.45moles used to neutralize excess acid
d) 18.3 g, 19.9 mL. Molarity of NaOH= (18.3gX1000)/19.9mLX40=22.9M.Hence moles of NaOH used to neutralize excess acid=22.9MX19.9mL/1000=0.4557 moles.
e) 17.5 g, 24.4 mL. Molarity of NaOH= (17.5gX1000)/24.4X40=17.9M. Hence moles of NaOH used to neutralize excess acid=17.9M X24.4mL/1000=0.43368moles.
From the calculation we see that for b tablet where 21.0 g, 22.4 mL (0.5251moles) of sodium hydroxide was used to neutralize the remaining acid was the weakest antacid while tablet e (17.5 g, 24.4 mL or 0.4368moles of NaOH) was used to neutralize the remaining acid was the strongest antacid.
2. Which are the strongest and weakest, on a by-weight? We use the equation E=N/W where W=mass of tablet in weight and E=mass effectiveness and N=number of moles of acid neutralized by tablet.
3. To observe color change, phenophetaline can be used.
4. Any solution can be deemed neutral at pH 7.0
5. in case when you have only 0.1M sulphuric acid to carry out the experiment. From the reaction of NaOH and sulphuric acid, we get:
2NaOH +H2SO4 Na2so4 +2H2O. We see that the mole ration of NaOH: H2SO4 is 2:1 respectively and therefore we calculating we bear in mind that for every one 1 mole of sulphuric acid consumed, 2 moles of sodium hydroxide is required.
6. Al (OH)3 + 3HCI %uF0E0 AlCl3 + 3H20
Back-titration was achieved by weighing each antacid tablet and mixing with 40 mL of 0.1 M HCl in separate Erlenmeyer flask. Then this was followed by adding different concentrations of sodium hydroxide drop-by-drop to back-titrate the solution until the pH was neutral. It was found out that mass of active ingredient in the tablet determines the amount of acid that will be neutralized by it. When a tablet has higher concentration of active ingredient less sodium hydroxide is used and it is cost effective. Therefore, the objective of the experiment was met.