Question
A 0.879 g sample of a CaCl2 ∙ 2 H2O / K2C2O4 ∙ H2O solid salt mixture is dissolved in 150 mL of
deionized water. A precipitate forms which is then filtered and dried. The mass of this precipitate is
0.284 g. The limiting reagent in the salt mixture was later determined to be CaCl2 ∙ 2 H2O.
(a) Write the molecular form of the equation for the reaction. (2)
(b) Write the net ionic equation for the reaction (3)
(c) How many moles of CaCl2 ∙ 2 H2O reacted in the reaction mixture? (2)
(d) How many grams of CaCl2 ∙ 2 H2O reacted in the reaction mixture? (2)
(e) How many moles of K2C2O4 ∙ H2O reacted in the reaction mixture? (1)
(f) How many grams of K2C2O4 ∙ H2O reacted in the reaction mixture? (1)
(g) How many grams of K2C2O4 ∙ H2O in the salt mixture remain unreacted? (2)
(h) What is the percent by mass of each salt in the mixture?
deionized water. A precipitate forms which is then filtered and dried. The mass of this precipitate is
0.284 g. The limiting reagent in the salt mixture was later determined to be CaCl2 ∙ 2 H2O.
(a) Write the molecular form of the equation for the reaction. (2)
(b) Write the net ionic equation for the reaction (3)
(c) How many moles of CaCl2 ∙ 2 H2O reacted in the reaction mixture? (2)
(d) How many grams of CaCl2 ∙ 2 H2O reacted in the reaction mixture? (2)
(e) How many moles of K2C2O4 ∙ H2O reacted in the reaction mixture? (1)
(f) How many grams of K2C2O4 ∙ H2O reacted in the reaction mixture? (1)
(g) How many grams of K2C2O4 ∙ H2O in the salt mixture remain unreacted? (2)
(h) What is the percent by mass of each salt in the mixture?
Answers
DrBob222
This looks straight forward to me but I'll get you started.
a. CaCl2.2H2O + K2CrO4 ==> CaCrO4 + 2KCl + 2H2O
b. Ca^2+ + CrO4^2- ==> CaCrO4
c. mols CaCrO4 = grams CaCrO4/molar mass CaCrO4 = ?. g = 0.284
Since 1 mol CaCl2.2H2O = 1 mol K2CrO4 in the reaction, mols CaCl2.2H2O = mols CaCrO4
d. g CaCl2.2H2O = mols CaCl2.2H2O x molar mass CaCl2.2H2O = ?
e. You see how it's done. I'll let you finish. Post your work if you get stuck.
a. CaCl2.2H2O + K2CrO4 ==> CaCrO4 + 2KCl + 2H2O
b. Ca^2+ + CrO4^2- ==> CaCrO4
c. mols CaCrO4 = grams CaCrO4/molar mass CaCrO4 = ?. g = 0.284
Since 1 mol CaCl2.2H2O = 1 mol K2CrO4 in the reaction, mols CaCl2.2H2O = mols CaCrO4
d. g CaCl2.2H2O = mols CaCl2.2H2O x molar mass CaCl2.2H2O = ?
e. You see how it's done. I'll let you finish. Post your work if you get stuck.
Doc48
DrBob, The chemistry is correct but, where did the chromate come from? I think you meant potassium oxalate monohydrate. :-)
DrBob222
Oh Crud!!. I just misread C2O4 as CrO4. But that doesn't change any of the numbers or equation. Thanks for pointing that out. My eyesight is getting really bad. Even with proofing I still made the mistake.
Doc48
Ya got plenty of wins! Not to worry. :-)