Scientists and Experiments
3 Basic Laws
Moles and Molar Mass
Isotopes
Mass, Moles, and # of Atoms
100
1. The ancient Greek natural philosopher that first proposed the notion of the atom was
a. Aristotle.
b. Socrates.
c. Democritus.
d. Plato.
What is c?
100
6. The atomic mass of an atom of carbon is 12 amu, and the atomic mass of an atom of oxygen is 16 amu. To produce CO, 16 g of oxygen combine with 12 g of carbon. To produce CO2, 32 g of oxygen combine with 12 g of carbon. The ratio of the mass of oxygen in CO2 to the mass of oxygen in CO is
a. 1:1.
b. 2:1.
c. 1:2.
d. 8:3.
What is b?
100
11. Compared with a mole of lead atoms, a mole of iron atoms
a. has more atoms.
b. has fewer atoms.
c. has the same number of atoms.
d. cannot be determined because iron is magnetic.
What is c?
100
16. Carbon-14 has 8 neutrons. What is the atomic number of carbon-14?
What is 6?
100
21. Avogadro's Number
What is 6.022 x 1023?
200
2. Thomson's experiment showed that the charge-to-mass ratio of electrons was
a. greater with noble gases than for other gases.
b. less with noble gases than for other gases.
c. the same in all gases.
d. dependent on the element's atomic mass.
What is c?
200
7. The law of multiple proportions is demonstrated by the compounds
a. FeCl3 and Fe(SO4)3.
b. O2 and O3.
c. CO and CO2.
d. FeCl2 and Fe(NO3)2.
What is c?
200
12. The molar mass of an element is numerically equal to
a. the element's average atomic mass.
b. the element's average atomic number.
c. the number of electrons possessed by an element.
d. the percentage composition of the element by mass.
What is a?
200
17. The atomic number of nickel-60 is 28. How many neutrons does this isotope have?
What is 32?
200
22. How many moles are in a 63.60 g sample of carbon? (The molar mass of carbon is 12.01 g/mol.)
What is 5.296 mol?
300
3. Rutherford's gold-foil experiment led him to conclude that
a. Thomson's plum pudding model of the atom was accurate.
b. alpha particles were a poor choice for a bombardment material.
c. a dense region of positive charge existed somewhere in the atom.
d. light was emitted by electrons returning to ground state.
What is c?
300
8. According to the law of conservation of mass, when sodium, hydrogen, and oxygen react to form a compound, the mass of the compound will be
a. equal to the sum of the masses of the reactants.
b. greater than the sum of the masses of the reactants.
c. less than the sum of the masses of the reactants.
d. either less than or equal to the sum of the masses of the reactants.
What is a?
300
13. Which of the following is not equal to 1.00 mol of carbon-12?
a. 6.022 x 1023 carbon atoms
b. 12.0 g of carbon
c. 6.0 g of carbon
d. both (b) and (c)
What is c?
300
18. A neutral atom of silicon-30 contains 14 protons. How many electrons does it have?
What is 14?
300
23. The average atomic mass of chromium is 52.00 u. What is the mass of 3.00 mol of chromium?
What is 156 g?
400
4. Millikan's experiments led to the determination
a. that the electron carries no charge.
b. of the electron's positive charge.
c. of the approximate value of the electron's mass.
d. that the electron has no mass.
What is c?
400
9. According to the law of definite proportions, any two samples of KCl will have
a. the same mass.
b. slightly different molecular structures but the same two elements.
c. different densities.
d. the same elements in the same proportions by mass.
What is d?
400
14. The units of molar mass are
a. g/mol.
b. mol/g.
c. amu/mol.
d. amu/g.
What is a?
400
19. Explain why the atomic mass of a particular isotope of an element differs from the average atomic mass of that element.
Because it is just one isotope's mass and it is different from other isotope's masses of the same element. Therefore, it is different from the average atomic mass, which is an average of all of the isotope's masses.
400
24. The mass of a sample of nickel (average atomic mass 58.69 u) is 11.74 g. How many atoms does it contain?
What is 1.205 x 1023 atoms?
500
5. Dalton's theory agreed with the modern atomic theory in almost all cases. List the two statements that were later found to be in error.
All atoms of the same element have the same mass. Atoms cannot be subdivided.
500
10. If a particular compound is composed of elements A and B, the ratio of the mass of B to the mass of A will always be the same. This is a statement of the law of ________________.
What is definite proportions?
500
15. The amount of a substance that contains a number of particles equal to the number of atoms in exactly 12 g of carbon-12 is referred to as a(n) ______________.
What is mole?
500
20. Oxygen has 3 naturally occurring isotopes in the following proportions: oxygen-16, 99.762% (15.99491 u); oxygen-17, 0.038000% (16.99913 u); oxygen-18, 0.20000% (17.99916 u). What is the average atomic mass of oxygen?
What is 15.999 u?
500
25. The atomic mass of sulfur is 32.06 u. How many atoms are present in exactly 2 mol of sulfur?
What is 1.204 x 1024 atoms?
M
e
n
u