Part 3 – Exploring reactions and the law of conservation of mass Some reaction l

Question

Part 3 – Exploring reactions and the law of conservation of mass Some reaction lead to visible changes and some lead to invisible changes, but all reactions obey the law of conservation of mass…. 1. Measure out the following reagents using a graduated pipette fitted with a syringe for suction (like in Expt#1). Be sure to thoroughly rinse the pipette between reagents: a. Into a 10 mL Erlenmeyer flask, measure out 4 mL of 1 M sodium carbonate. b. Into a labeled test tube, measure out 1 mL of 1 M calcium chloride solution. c. Into a labeled test tube, measure out 1 mL of 3 M sulphuric acid. Weigh the flask and the two test tubes together in a 100 mL beaker on a top loading balance. Record the weight. Remove the beaker from the balance. Finally, note the initial appearance of the three solutions. 2. With the flask still in the beaker (necessary for catching overflow from the flask!), carefully pour the calcium chloride solution into the flask and swirl the contents to mix them. Note what happens. Weigh the three items (including the now empty test tube) in the same beaker again. 3. With the flask still in the beaker, slowly and carefully add the sulphuric acid to the flask while swirling the solution. Note what happens. Finally, weigh the flask and the two empty test tubes one more time in the beaker

Regarding Part 3: What conclusions can you draw from your observation of the reactions performed in the Erlenmeyer flask? Be careful to explicitly distinguish between speculations you cannot back up and speculations based on any chemistry that you may already have learned

Explanation / Answer

Na2CO3 + CaCl2 >> CaCO3 + 2 NaCl

One of the products of the reaction, sodium chloride, is soluble and will remain in solution. The other product CaCO3 forms a precipitate.

H2SO4(aq) + CaCO3(s)====>CaSO4(s) + H2O(l) + CO2(g)

Bubbles of Carbon dioxide and a white precipitate of CaSO4 forming. Some heat will be evolved

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