# CHEM 1120 Experiment 4: Pigment Synthesis

Which reaction is occurring in the test tube?

Select one:
Mg(s) + HCl(aq) ⟶ MgCl2(aq) + H2(g)
HBr(aq) + LiOH(aq) ⟶ LiBr(aq) + H2O(l)
KCl(aq) + AgNO3(aq) ⟶ AgCl(s) + KNO3(aq)
C(s) + O2(g) ⟶ CO2(g)
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KCl(aq) + AgNO3(aq) ⟶ AgCl(s) + KNO3(aq)

The image shows a precipitation, in which a solid product is formed from two reactant solutions. Thus, the reaction equation matching the test tube in the image needs to have aqueous reactants on the left side of the reaction arrow and a solid product on the right side of the reaction arrow. Determine whether each observation generally corresponds to a physical change or a chemical change.

A solution heats up upon mixing with another.
A solid dissolves into water.
Bubbles are produced upon mixing two solutions.
A precipitate is formed from two solutions.
A liquid freezes into a solid.
The color of a substance changes over time.
The molar mass of a hydrate compound is the molar mass of the ionic compound plus the molar mass of water multiplied by the number of waters of hydration in the formula. Determine the molar masses of CrCl3 and H2O by adding up the individual molar masses of the elements from the periodic table. Then, multiply the molar mass of water by the number of waters in the formula, which is 3 , and add the molar mass together.

molar mass of CrCl3⋅3H2O = molar mass of CrCl3 +( 3) (molar mass of H2O)

molar mass of CrCl3⋅3H2O = 158.36 g/mol + (3) (18.02 g/mol)

molar mass of CrCl3⋅3H2O = 212.42 g/mol
When preparing for work in the fume hood, be sure to gather all necessary tools, glassware, and chemicals (???) to minimize the number of times the hood sash is raised and lowered.
Work as much as possible in the (???) of the work surface to keep the area tidy and promote air flow.
If you need to step away from the experiment to obtain another item, (???) the sash during this time.
When preparing for work in the fume hood, be sure to gather all necessary tools, glassware, and chemicals in advance to minimize the number of times the hood sash is raised and lowered.
Work as much as possible in the middle of the work surface to keep the area tidy and promote air flow.
If you need to step away from the experiment to obtain another item, lower the sash during this time.
When balancing a redox reaction, begin by separating the reaction into half reactions. Balance each of these in terms of atoms and charge. Multiply by some factor if necessary so that the number of electrons appearing in both is the same. Add these together, canceling out any terms that appear on both sides of the final equation.