Question 20 (essay worth 8 points)
(04.01 mc)
a chemical equation is shown below.
fecl3 + naoh → nacl + fe(oh)3
what are the coefficients that should be added to balance this equation? use complete sentences to explain your answer.
explain how this chemical reaction demonstrates the conservation of mass.
question 21 (essay worth 8 points)
(04.03 mc)
part 1: name the type of chemical reaction that occurs when calcium hydroxide (ca(oh)2) reacts with nitric acid (hno3).
part 2: explain why zinc (zn) would react with lead nitrate (pbno3) but not with calcium chloride (cacl2).
question 22 (essay worth 8 points)
(04.07 hc)
the table shows the amount of radioactive element remaining in a sample over a period of time.
radioactive decay rate
amount of radioactive sample
(grams) time
(hours)
186.0 0
147.0 7
117.0 14
93.0 21
23.3 63
part 1: what is the half-life of the element? explain how you determined this.
part 2: how long would it take 320 g of the sample to decay to 2.5 grams? show your work or explain your answer.