Which of the following would be classified as a pure substance(s)? a) elements b

Question

Which of the following would be classified as a pure substance(s)? a) elements b) compounds c) pure water d) carbon dioxide e) all of these Aqueous solutions of ammonium phosphate and calcium chloride are mixed together. When the chemical equation is balanced using the smallest possible integers, what is the sum of all coefficients? a) 8 b) 9 c) 10 d) 11 c) 12 A sample of oxygen gas has a volume of 4.50 L at 27 degree C and 800.0 torr. How many oxygen molecules does It contain? a) 1.16 times 10^23 b) 5.8 times 10^22 c) 2.32 times 10^24 d) 1.15 times 10^22 e) None of these Aqueous solutions of sodium sulfide and copper(II) chloride are mixed together. Which statement is correct? a) Both NaCI and CuS precipitate from solution. b) No precipitate forms. c) CuS will precipitate from solution. d) NaCI will precipitate from solution. e) No reaction will occur. Which of the following compounds is insoluble in water? a) Na_2 S b) K_3 PO_4 c) Pb(NO_3)_2 d) CaCl_2 e) All of these are soluble in water Given the following reaction, suppose 2 moles of A are reacted with 1 mole of B. Which of the following is true? 3A + B rightarrow C + D a) A is the limiting reactant because of Its higher molar mass. b) A is the limiting reactant because you need 3 moles of A and have 2. c) B is the limiting reactant because you have fewer moles of B than A. d) B is the limiting reactant because 3 A molecules react with 1 B molecule. e) Neither reactant is limiting.

Explanation / Answer

7.All of these are pure substances.Pure substances are made of the same material throughout and have the same properties throughout.Pure substances cannot be separated into other substances.Elements are pure substances that can not be made from or broken down into simpler pure substances by ordinary physical or chemical method.Compounds are also pure substances made of two or more different elements in combination.e.g.water,carbon dioxide

8.(e) 12

2(NH4)3PO4 + 3CaCl2 -----> Ca3(PO4)2 + 6NH4Cl

Sum of all coefficients= 2+3+1+6 =12

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