Mass Spectra Of Elements

In the mass spectrum of an element, what does the height of a peak represent?

A mass spectrum of an element displays peaks at m/z = 24, 25, and 26. How many naturally occurring isotopes does this element have?

Gallium has two stable isotopes: ⁶⁹Ga with a mass of 68.93 amu and 60.11% abundance, and ⁷¹Ga with a mass of 70.92 amu and 39.89% abundance. Calculate the average atomic mass of gallium.

An element has two isotopes with masses of 107 amu and 109 amu. The mass spectrum shows the peak at 107 is roughly equal in height to the peak at 109, but very slightly taller. Which value best estimates the average atomic mass?

A student calculates the average atomic mass of chlorine by computing (34.97 + 36.97) ÷ 2 = 35.97 amu. The accepted value is 35.46 amu. Which statement best explains the student’s error?

Magnesium has three stable isotopes: ²⁴Mg (23.99 amu, 78.99%), ²⁵Mg (24.99 amu, 10.00%), and ²⁶Mg (25.98 amu, 11.01%). Calculate the average atomic mass of magnesium.

A researcher discovers a new element with two isotopes. Isotope A has a mass of 220.0 amu, and isotope B has a mass of 224.0 amu. The average atomic mass is found to be 221.0 amu. Determine the fractional abundance of isotope A.

Copper’s mass spectrum shows a peak at m/z = 63 with 69.2% relative abundance and a peak at m/z = 65 with 30.8% relative abundance. A student claims the average atomic mass of copper is 64.0 amu. Evaluate this claim.

Element X has three isotopes. Its mass spectrum shows a very tall peak at m/z = 40, a tiny peak at m/z = 42, and a very tiny peak at m/z = 44. Without performing a calculation, which range most likely contains the average atomic mass of element X?

A student is given that bromine has two isotopes: ⁷⁹Br (78.92 amu) and ⁸¹Br (80.92 amu). The periodic table lists bromine’s average atomic mass as 79.90 amu. Calculate the percent abundance of ⁷⁹Br.

A geologist analyzes a rock sample and finds that the strontium within it shows a mass spectrum with a peak at m/z = 88 that is twice the height of a peak at m/z = 86, with negligible peaks at other masses. She uses these two isotopes to estimate the average atomic mass. If ⁸⁸Sr has a mass of 87.91 amu and ⁸⁶Sr has a mass of 85.91 amu, what is the estimated average atomic mass from these data?

An AP Chemistry student examines a mass spectrum and sees four peaks. She concludes the sample contains four different elements. Identify the flaw in her reasoning.

Lithium has two stable isotopes: ⁶Li (6.015 amu, 7.59%) and ⁷Li (7.016 amu, 92.41%). A student performs the calculation (6.015 × 7.59) + (7.016 × 92.41) and obtains 693.7. What error did the student make, and what is the correct average atomic mass?

An element has two isotopes. Isotope P has mass 191.0 amu and isotope Q has mass 193.0 amu. The average atomic mass is 192.2 amu. What is the percent abundance of isotope Q?