Each question is followed by up to five lettered responses (A-E). For each question choose the response which is the best answer to the question.

1. The mass spectrum of an element is as shown below.
   
   Assuming each fragment has unit charge, what is the relative atomic mass of the element?
   

   1.   ?     206.25
   2.   ?     208.00
   3.   ?     207.77
   4.   ?     207.00
      

2. The mass spectrometer trace for naturally occurring magnesium is shown below.
   
   
   Assuming that all three peaks relate to ions with one positive charge, what is the relative atomic mass for magnesium?
   
   

   1.   ?    24.7
   2.   ?     24.3
   3.   ?    24.1
   4.   ?    24.5

3. The accurate relative isotopic masses of five isotopes are
   ¹₁H = 1.0078   ²₁H = 2.0141   ¹²₆C = 12.000   ¹⁴₇N = 14.0031   ¹⁶₈O = 15.9949
   Using a high resolution mass spectrometer, a certain gas was found to have a relative molecular mass of 28.0172. The gas could be
   
   
   

   1.   ?     ¹²₆C₂ ¹₁H₄
   2.   ?     ²₁H ¹²₆C ¹⁴₇N
   3.   ?     ¹²₆C₂ ²₁H₂
   4.   ?     ¹⁴₇N₂

4. The isotopic composition of a certain element X is 80% ²⁴X, 10% ²⁵X and 10% ²⁶X.
   The relative-atomic mass of X is
   
   

   1.   ?    24.33
   2.   ?    24.25
   3.   ?    24.67
   4.   ?    24.30

5. Which one of the following could not be obtained using a mass spectrometer?
   

   1.   ?    The number of isotopes present in a sample of chlorine
   2.   ?    The number of electrons in an isotope of manganese
   3.   ?    The relative molecular mass of a sample of cocaine
   4.   ?    The mass of an isotope of uranium

6. The diagram below shows the mass spectrometer trace of the substance X in the region of relative mass 10 to 20 units.
   
   
   Which of the following substances is X most likely to be?
   
   

   1.   ?    H₂O
   2.   ?    O₂
   3.   ?     CH₄
   4.   ?     NH₃

7. Using a mass spectrometer, it is possible to determine the number of
   

   1.   ?    neutrons in an atom
   2.   ?    protons in an atom
   3.   ?    isotopes of an element
   4.   ?    energy levels in an atom