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3.E: Composition of Substances and Solutions- Homework

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    428698

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    For Chapter 3 you MUST know:

    • The additional polyatomic ions: cyanide ( \(\ce{CN^-}\)), nitrite ( \(\ce{NO_2^-}\)), and sulfite ( \(\ce{SO_3^{2-}}\)).

    Turn in your answers for the following questions - show your work

    1. For the following molecules; write the chemical formula, determine the molecular weight and determine the number of moles in exactly 1 gram.
      1. carbon dioxide
      2. iron (II) chloride
      3. dinitrogen pentoxide
      4. iron (III) sulfate
    2. Name the following compounds, determine the molecular weight and determine how many moles in 8.35 grams of the compound.
      1. KI
      2. CaF2
      3. Cu2SO4
      4. N2O
      5. LiOH
    3. Give the chemical formula (or atomic symbol), molecular (or atomic) weight, and charge for the following ions:
      1. sulfate
      2. sulfite
      3. nitrate
      4. chloride
      5. nitride
      6. acetate
      7. carbonate
    4. Calculate the number of moles in:
      1. 45.3594 g of Ne
      2. 0.198669 g of Ne
    5. Calculate the mass of:
      1. 2.00 mole of Fe
      2. 4.362 x 10-5 mol of Fe
    6. Describe how to prepare 250 mL of 0.12 M lithium chloride solution from solid lithium chloride.
    7. Describe how to prepare 100 mL of 0.012 M lithium chloride solution from a 0.12 M lithium chloride solution.

    The Following Questions are for your practice - Do Not Turn In.  They include answers so you can check your work

    3.1: Formula Mass and the Mole Concept

    1. What is the total mass (amu) of carbon in each of the following molecules?
      1. CH4
      2. C12H10O6
      (a)
      12.01 amu
      (b)
      144.12 amu
    2. Calculate the molecular or formula mass of each of the following:
      1. P4
      2. H2O
      3. Ca(NO3)2
      (a)
      123.896 amu
      (b)
      18.015 amu
      (c)
      164.086 amu
    3. Determine the molecular mass of the following compounds:
      1. A structure is shown. Two C atoms form double bonds with each other. The C atom on the left forms a single bond with two H atoms each. The C atom on the right forms a single bond with an H atom and with a C H subscript 2 C H subscript 3 group.
      2. A structure is shown. There is a C atom which forms single bonds with three H atoms each. This C atom is bonded to another C atom. This second C atom forms a triple bond with another C atom which forms a single bond with a fourth C atom. The fourth C atom forms single bonds with three H atoms each.
      (a)
      56.107 amu
      (b)
      54.091 amu
    4. Calculate the molar mass of each of the following:    
      1. S8
      2. C5H12
      (a)
      256.528 g/mol
      (b)
      72.150 g mol−1
    5. Determine the mass of each of the following:
      1. 0.0146 mol KOH
      2. 10.2 mol ethane, C2H6
      (a)
      0.819 g
      (b)
      307 g

    3.2: Determining Empirical and Molecular Formulas

     
    answer
    Mg3Si2H3O8 (empirical formula), Mg6Si4H6O16 (molecular formula)
    1. Calculate the percent composition of ammonia, NH3 to four significant figures:
      answer
      % N = 82.24%; % H = 17.76%
    2. A compound of carbon and hydrogen contains 92.3% C and has a molar mass of 78.1 g/mol. What is its molecular formula?
      answer
      C6H6
    3. Determine the empirical and molecular formula for chrysotile asbestos. Chrysotile has the following percent composition: 28.03% Mg, 21.60% Si, 1.16% H, and 49.21% O. The molar mass for chrysotile is 520.8 g/mol.

    3.3: Molarity

    1. Determine the molarity for 0.444 mol of CoCl2 in 0.654 L of solution
      answer
      0.679 M
    2. Determine the molarity for 98.0 g of phosphoric acid, H3PO4, in 1.00 L of solution
      answer
      1.00 M
    3. Calculate the number of moles and the mass of the solute in 2.00 L of 18.5 M H2SO4, concentrated sulfuric acid:
      answer
      37.0 mol H2SO4; 3.63 × 103 g H2SO4
    4. Calculate the molarity of 0.195 g of cholesterol, C27H46O, in 0.100 L of serum, the average concentration of cholesterol in human serum
      answer
      5.04 × 10−3 M
    5. What is the molarity of the diluted solution when 1.00 L of a 0.250-M solution of Fe(NO3)3 is diluted to a final volume of 2.00 L?
      answer
      0.125 M
    6. What volume of a 0.20-M K2SO4 solution contains 57 g of K2SO4?
      answer
      1.6 L

    This page titled 3.E: Composition of Substances and Solutions- Homework is shared under a CC BY license and was authored, remixed, and/or curated by Scott Van Bramer.