2. The idea that we could measure the mass of one atom in comparison to another – relative mass – was probably invented by:
a) Dalton     b) Avogadro    c) Loschmidt    d) Gay-Lussac    e) Cannizzaro

3. The idea that we should use the hydrogen atom as the reference standard for doing relative mass comparisons came from
a) Dalton     b) Avogadro    c) Loschmidt    d) Gay-Lussac    e) Cannizzaro

4. Which of the following do you need to know in order to do a relative mass comparison?
a) the actual mass of one unit of the lighest substance
b) the actual number of objects whose masses are being compared
c) that there are the same number of objects in each mass that is being compared
d) none of the above

5. Which of the following is the correct unit for atomic mass?
a) g     b) moles     c) micrograms     d) none of the above

6. When doing a relative mass comparison you would normally compare each mass:
a) to the heaviest object
b) to the middle object
c) to the lightest object
d) none of the above

7. The idea that lets us do relative mass comparisons by using equal volumes of gases originated with:
a) Dalton     b) Avogadro    c) Loschmidt    d) Gay-Lussac    e) Cannizzaro

8. Which of the following is a correct statement of Avogadro's hypothesis?
a) equal amounts of gases have the same mass
b) equal volumes of gases have the same numbers of atoms
c) any gases at the same temperature and pressure have an equal volume
d) none of the above

9. Why is Avogadro's hypothesis considered so important in Chemistry?
a) it contradicted the idea of John Dalton
b) it provided a way of calculating atomic masses
c) it was proven to be true more than 150 years ago
d) none of the above

10. A 5 litre flask is filled with hydrogen at room conditions (25 ^oC and 1 atmosphere pressure).  Its mass is measured, and then the flask is emptied, and filled with an unknown gas X at the same conditions.  Here are the observed results.

What is the mass of gas X relative to hydrogen?
a) 0.0631     b) 0.945    c) 1.06    d) 15.85    e) 110.82

11. The calculation in the above question is only possible because (check all that apply):
a) we know the exact volume of the flask
b) the size of the flask, the temperature and the pressure are the same
c) we accept Avogadro's hypothesis
d) we know the actual atomic mass of hydrogen

12. A flask is first filled with oxygen, then with an unknown gas Y.  The pressure and temperature are kept constant.  The empty flask has a mass of 103.21 g.  When full of oxygen its mass is 103.85 g.  When full of gas Y it has a mass of 103.94 g.  What is the relative mass for gas Y compared to oxygen?

a) 0.640    b) 0.730    c) 1.00    d) 1.14     e) 103.94

13. If the actual relative mass of an oxygen molecule is 32.0, then to three significant figures the mass of gas Y in the above question is actually    

14. On a modern atomic mass scale, the mass of natural hydrogen is 1.0079.  Why is the mass of hydrogen not exactly 1.0 (check all that apply)?
a) natural hydrogen is a mixture of isotopes
b) a hydrogen atom has a real mass of 1.0079 x 10 ^-28 g
c) on the modern atomic mass scale, atoms are compared to carbon-12, not hydrogen
d) on the modern atomic mass scale, atoms are compared to naturally occuring oxygen-16
e) Carbon-12 is assigned a mass of exactly 12.  However, because of binding energy, carbon-12 is actually lighter than the mass of 6 independent protons and 6 independent neutrons.  Therefore it is less than 12 times as heavy as 1 hydrogen atom.

15. Suppose that an element X was made of two naturally occuring isotopes with the following abundances and relative masses: