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GOB Chemistry Fundamentals

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Terms in this set (13)

  • If a substance can be decomposed, is it an element or a compound?

    It is a compound because elements cannot be decomposed into simpler substances.
  • If a substance conducts electricity when dissolved in water, how is it classified?

    It is classified as an ionic compound (or electrolyte).

  • State the law of definite proportions in your own words.
    A chemical compound always contains the same elements in exactly the same proportions by mass.

  • Why is the chemist wrong to say "compound a" (14.0 g N + 16.0 g O) and "compound b" (42.0 g N + 48.0 g O) are two completely different compounds?

    Both experiments use the exact same mass ratio of nitrogen to oxygen (14.0 g : 16.0 g is the same 7:8 ratio as 42.0 g : 48.0 g, just multiplied by 3). By the law of definite proportions, they can be the exact same compound.

  • If a substance is brittle and does not conduct electricity, is it likely a metal or a nonmetal?
    It is most likely a nonmetal, as metals are typically malleable and conduct electricity.
  • Which theory of matter do scientists believe today: discontinuous or continuous?
    Scientists support the discontinuous theory of matter, meaning matter is made of discrete atoms.

  • All scientists today believe that atoms do, in fact, exist. Has their existence been proven?

    No. Science cannot prove anything with 100% certainty, so the existence of atoms has not been proven, even though overwhelming experimental evidence supports it.

  • A substance decomposes into 12.1 g carbon and 40.0 g magnesium from 100.1 g total. What is the mass of oxygen gas lost?
    Mass of oxygen = 100.1 g - (12.1 g + 40.0 g) = 48.0 g.
  • How to make 100.0 g of sulfur trioxide with no leftover oxygen if 32.0 g S + 50.0 g O make 80.0 g SO3 with 2.0 g leftover O?
    Use the ratio: 32.0 g S : 80.0 g SO3 = 40.0 g S for 100.0 g SO3; oxygen needed = 50.0 g - 2.0 g leftover = 48.0 g scaled to 60.0 g O.

  • If 12.0 g C + 32.0 g O makes 44.0 g CO2, how much CO2 is made from 120.0 g C and 160.0 g O, and what is left over?

    220.0 g of CO2 will be made, with 60.0 g of carbon left over. (160.0 g O is 5 times 32.0 g O, so it reacts with 5 x 12.0 g = 60.0 g C to make 5 x 44.0 g = 220.0 g CO2, leaving 120.0 g - 60.0 g = 60.0 g C unused.)

  • If a molecule has 17 atoms and formula C5H10Clx, what is x?
    Total atoms = 5 + 10 + x = 17, so x = 2 chlorine atoms.
  • Which atoms are nonmetals: W, Ne, Xe, Mn, Fe, S?
    Ne, Xe, and S are nonmetals; W, Mn, and Fe are metals.
  • Which compounds conduct electricity when dissolved in water: C3H6ClF, NaNO3, CS2, BaSO4?

    NaNO3 and BaSO4, because they are ionic compounds (formed from a metal and nonmetals), whereas C3H6ClF and CS2 are covalent (nonmetals only) and do not conduct electricity. (Note: In practice, BaSO4 is poorly soluble.)