INVESTIGATING STOICHIOMETRY WITH SODIUM SALTS OF CARBONIC ACID
In this experiment we are going to get a better understanding of chemical stoichiometry. We are going to be reacting sodium bicarbonate (NaHCO3) and sodium carbonate (Na2CO3) with hydrochloric acid (HCl). To start off the mass of two unknown substances (being the sodium bicarbonate and sodium carbonate) will be taken. We will need to construct balanced equations for both of the reactants with the HCl and use this to guide us to figure out how much HCl will be needed to react with each of the unknown substances. When this part is through we will then need to find the percent yield (actual yield/theoretical yield x 100). Determining the mass of sodium chloride at the end of the experiment is the actual yield. To find the theoretical yield we will need to heat the sodium chloride so that all the CO2 evaporates and that will leave us with the theoretical yield of sodium chloride.
NaHCO3 + HCl = NaCl + H20 + CO2
Na2CO3 + HCl = 2NaCl + H2O + CO2
.15g NaHCO3 (1mol NaHCO3/84.0059g NaHCO3) (1mol HCl/1mol NaHCO3) (58.44gNaCl/1molNaCl) = .1043 g NaCl
.15g Na2CO3 (1mol Na2CO3/105.988g Na2CO3) (1mol HCl/1mol Na2CO3) (58.44gNaCl/1molNaCl) = .165 g NaCl
Standardization of Unknown 1
1) Weigh duplicate 0.15 g samples of unknown 1. Dissolve samples in 100- ml distilled water.
2) Add bromocresol green indicator, until the solution turns into blue. Titrate it with HCl until green color is reached.
3) Heat and boil out CO2 gently. You should obtain a blue color again at the end of this step. Cool to room temperature, and continue titration until yellow color is reached. Note down the volume seen on the buret.
4) Heat the substance again until all the liquid is gone and you’re left with salt looking particles inside the beaker.
5) Weigh the beaker with the salt inside of it. Then, clean out the beaker thoroughly