# Molar solutions

- Introduction
- Changes in the volume of the reactant
- The mole ratio formula
- Calculating the amount of precipitate
- Materials for experiment
- The procedure
- Observation
- Experimental errors
- Conclusion

Before the experimenting phase of the lab, the students must first calculate the molarity of the given solutions so that exact reacting ratio will occur between the two solutions when mixed. One reactant will be constant, as in each lab the molarity and the volume of that reactant will remain the same. The other reactant, however, will vary. The volume of the reactant will change during every reaction for it's the independent variable in the lab and the objective of this lab is to study how the change in molarity affects the amount of product that will form. The product is the substance that forms from the reaction of the two reactants. Some information is given, such as the molarity and volume of the constant reactants and the volume of the varying reactant. The problem is to calculate the unknown molarity of the varying reactant. But before any calculations should be done, the first concept that needs to be understood is ?exact reacting ratio'. Exact reacting ratio is when two solutions are combined, the ratio of moles are perfect so that both reactants will completely react. But if the mole ratio isn't perfect and the number of moles of each reactant has isn't proportional, then during the reaction, one of the chemicals will get used up before the other one.

[...] Before the experiment, the students must make their respective molar solutions. But first, they need to figure out how much of Na2SO4 is required to make their molar solutions, and they calculate this by using the following formula: 100.ml solution X 1 Liter sol. X amount of mole(molarity) X 322.25 g 1000.ml sol 1 Liter 1 mole Na2So4+10H2O In this experiment, the students are also trying to predict the amount of precipitate, or the substance that will fall out of solution during a reaction, that will form after the reaction. [...]

[...] The experimental phase of the lab starts out requiring the students to make molar solutions of their respective molarity of Na2SO4+10H2O solution. After finding the amount of Na2SO4+10H2O necessary for their molar solutions (see calculations), the student will then make their molar solution. In my case, I had to make a 100ml 0.0200 M solution of Na2SO4+10H2O. I calculated the amount of Na2SO4 needed for 0.0200 moles of Na2SO4+10H2O in 100.ml solution was 0.644 grams (see calculations), I massed the Na2SO4+10H2O to that amount, and poured it into a 100ml volumetric flask. [...]

[...] While we all massed the correct amount of Na2SO4+10H2O needed for each of our solutions grams of Na2SO4+10H2O measured on one quadruple beam balance might be slightly heavier or lighter that another quadruple beam balance. And 1.84 grams of SrSO4 massed on one quadruple beam balance might not yield the same results on another balance. So the use of different quadruple beam balance made our results inconsistent and unreliable considering the results were measured with different balances. A way to prevent it in the future is for all students to use one balance for the whole lab, that way, all the results would have came from one source and at least the data would be consistent. [...]