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  • Questions 01-03:

    An experiment is conducted in order to determine the mass of silver metal in an alloy. The alloy is dissolved in acid to convert all of the silver metal to silver ions, and those ions are then precipitated by reaction with excess sodium chloride. The precipitate is washed, dried and weighed, and the following data are collected.

    Mass of silver alloy = 4.3148 g
    Mass of filter paper = 0.50000 g
    Mass of filter paper and dried precipitate 1.9332 g

    Question 01:

    Identify the precipitate and the number of moles of it produced in the gravimetric analysis?

  • Question 02:

    What is the % by mass of silver in the alloy?

  • Question 03:

    At the end of the experiment it is found that the actual (real) % of silver in the alloy is lower than the % calculated from the experimental data. Which of the following is the most likely explanation for the difference between the actual (real) value, and the calculated value?

  • Question 04:

    The complete combustion of one mole of a hydrocarbon in oxygen, yields carbon dioxide and water in a molar ratio of 3CO2 : 4H2O. What is a possible formula for the hydrocarbon?

  • Questions 06-07:

    When 2.299 g of sodium are brought together with 2.000 g of fluorine and the reaction below occurs.

    2Na(s) + F2(g) → 2NaF(s)

    Question 05:

    What is the maximum mass of sodium fluoride that can be produced?

  • Question 06:

    When the reaction is repeated, this time introducing 1.000 mole of Na metal with 0.5000 moles of F2 gas, it is found that 21.00 g of NaF are produced. What is the percentage yield in this experiment?

  • Question 07:

    Consider the combustion of ammonia shown in the equation below. Which of the following statements is true in relation to this reaction?

    4NH3 + 5O2 ⇒ 4NO + 6H2O

  • Question 08:

    A 100. mL sample of 0.100 M Li2CO3 solution is poured into a beaker that contains to 50.0 mL of 0.300 M Ba(NO3)2 solution. A precipitate is observed. Which of the following correctly predicts the contents of the beaker at the end of the reaction?

  • Question 09:

    What type of interaction (force or bond) is changed when solid magnesium chloride is melted?

  • Question 10:

    Chemical changes always involve the breaking of which type of interaction (force or bond)?

  • Question 11:

    How might one recognize a change as being purely a physical one?

  • Question 12:

    What type of change takes place when solid sodium chloride is dissolved in distilled water?