Give answers with units and to correct significant figures.
1) How many years are there in 1 mole of seconds? Use conversion factors, and show which units cancel. 6.022 x 10^23 sec x 1 min/60 sec/ 1 hr/60 min/1 day/24 hr/1 yr/365 days = 6.022 x 10 ^23 sec 1.004 x10 ^23/60 sec/1.673 x 106
2) Calculate the number of particles in each of the following:
(a) 0.125 mole zinc atoms, Zn 0.125mole zn/ 1 mole x 65.39 zn = 8.17375 or 81.74 g zinc
(b) 0.250 mol chlorine molecules, Cl2 0.250 mole cl/1 mole x 70.9 cl
(c) 0.675 mole zinc chloride formula units, ZnCl2
3) Calculate the molar mass for each of the following.
(a) calcium sulfide, CaS
(b) calcium sulfate, CaSO4
(c) glycerin, C3H5(OH)3
4) For element X, 59.8 g corresponds to 2.6 moles. What is the atomic mass of the element?
5) The formula C6H12O6 is a source of many conversion factors. Write at least three of them.
6) How many moles of Al atoms are needed to combine with 0.565 mol of O atoms to make aluminum oxide, Al2O3?
7) If you have 44.6 g of carbon tetrachloride, how many atoms of chlorine do you have?
8) How many grams of sulfur hexafluoride would you need to have 5.25 x 1024 fluorine atoms?
9) Some calcium supplements contain calcium citrate, Ca3(C6H5O7)2, and others contain calcium carbonate, CaCO3. Which compound has the higher mass percent of calcium? (Show your work to support your answer.)
10) From a 1.015 g sample of a binary compound of calcium and bromine, there was obtained 0.2035 g of Ca. Calculate the mass percent for each element in the compound and determine its empirical formula.
11) A substance is found experimentally to be 59.6% chlorine and 40.4% oxygen.
(a) What is the empirical formula?
(b) If the molar mass of the chlorine oxide is 356.7 g/mol, what is the molecular formula of the compound?
12) Which of the following is evidence for a chemical reaction?
(a) Heating purple iodine crystals produces a purple gas.
(b) Dropping sodium metal into water produces fizzing.
(c) Dissolving a white powder in solution gives white light.
(d) Mixing two colorless solutions gives a yellow solution.
13) Predict which of the following compounds are soluble in water:
(a) cobalt (II) hydroxide, Co(OH)2 ____________________________
(b) iron (II) sulfate, FeSO4 ____________________________
(c) silver chloride, AgCl ____________________________
(d) lead (II) acetate, Pb(C2H3O2)2 ____________________________
14) Give an anion that can be added in solution to separate:
(a) Na+(aq) from Ag+(aq)
(b) Na+(aq) from Ca2+(aq)
15) Write a balanced equation for each of the following double-displacement reactions. Include states:
(a) Aqueous solutions of chromium (III) iodide and sodium hydroxide react to give aqueous sodium iodide and a chromium (III) hydroxide precipitate.
(b) Aqueous solutions of nickel (II) sulfate and mercury (I) nitrate react to give aqueous nickel (II) nitrate and a mercury (I) sulfate precipitate.
16) Write a net ionic equation for the precipitation reaction, if any, that occurs when aqueous solutions of the following ionic compounds are mixed:
(a) Pb(NO3)2 and NaCl
(b) Ba(NO3)2 and NiSO4
(c) NaCl and KNO3
17) Write a balanced equation for each of the following neutralization reactions. Include states.
(a) Potassium hydroxide solution is added to phosphoric acid.
(b) Strontium hydroxide solution is added to acetic acid.
18) Which of the following are redox reactions?
(a) 2 Na + 2 H2O →2 NaOH+ H2
(b) MgBr2 + 2 NaF→MgF2 + 2 NaBr
(c) 2 CO + O2 →2 CO2
(d) SO2 + H2O →H2SO3
19) A 1.443 g sample of metal is reacted with excess oxygen to yield 1.683 g of the oxide M2O3. Calculate the atomic mass of the element M.
20) "Hard" water is hard because it contains Ca2+(aq) and Mg2+(aq) ions. It can be softened by adding borax powder, which is sodium tetraborate, Na2B4O7. Adding borax removes the Ca2+(aq) and Mg2+(aq) from solution. Write a net ionic equation for each of these two reactions. What ion replaces the Ca2+(aq) and Mg2+(aq) ions in the water?
21) Tap water contains dissolved oxygen gas, O2(aq). Adding heat to tap water causes the dissolved oxygen to leave. Which of the two equations below represents a chemical reaction, and which does not? Defend your answer.
(a) 2 H2O2(l) →2 H2O(l) + O2(g)
(b) H2O(l) + O2(aq)
Heat
H2O(l) + O2(g)