The law of fixed composition

Quiz: Dalton's Atomic Theory

1. Hydrogen combines with fluorine in a 1:19 weight ratio to form hydrogen fluoride. If every molecule of hydrogen fluoride contains one atom of hydrogen and one atom of fluorine, an atom of fluorine must weigh:

	1/19 times the mass of a hydrogen atom		19 times the mass of a hydrogen atom
	38 times the mass of a hydrogen atom		1/38 times the mass of a hydrogen atom

2. Dalton suggested that atoms were indestructible and unchangeble to explain:

	why elements combine in fixed weight ratios to form compounds
	why mass is conserved in chemical reactions
	why elements are characterized by the mass of their atoms
	why compounds combine in fixed weight ratios in chemical reactions

3. Hydrogen combines with nitrogen in a 3:14 weight ratio to form ammonia. If every molecule of ammonia contains three atoms of hydrogen and one atom of nitrogen, an atom of nitrogen must weigh:

	14 times the mass of a hydrogen atom		3 times the mass of a hydrogen atom
	3/14 times the mass of a hydrogen atom		14/3 times the mass of a hydrogen atom

4. Which of the following is not a postulate of Dalton's atomic theory?

	different elements have atoms of different masses
	chemical change is a rearrangement of atoms
	atoms are not created or destroyed in chemical change
	atoms of a single element can have different masses
	atoms combine in simple whole number ratios to form compounds

5. 1.008 grams of hydrogen combines with 35.453 g of chlorine to form 36.463 g of a pure compound (hydrogen chloride). Dalton's explanation for this experimental fact might be:

	one atom of hydrogen combines with 35.453 atoms of chlorine in this reaction
	hydrogen and chlorine atoms always combine in a 1:35 ratio.
	hydrogen and chlorine atoms aren't created or destroyed in the process so the reactant mass is the same as the product mass.
	this is a simple mixture of elements because the ratio isn't a whole number ratio
	chlorine accepts hydrogen's electron to form polar covalent hydrogen chloride

Dalton's Atomic Theory
Page 1: Introduction
Page 2: Dalton's assumptions Five steps forward and one step back.
Page 3: Atoms in compounds An "invisible hand" fixes atom ratios in compounds
Page 4: Atoms in reactions Dance of the atoms
Page 5: Learning check Take a quiz on Dalton's Atomic Theory
Page 6: References and resources

General Chemistry Online! Quiz