a. i. What do you understand by the term relative atomic mass? ii. A sample of boron

Question:

a. i. What do you understand by the term relative atomic mass?

ii. A sample of boron was found to have the following % composition by mass:

Calculate a value for the relative atomic mass of boron. Give your answer to 3 significant figures.

b. Boron ions, B³⁺, can be formed by bombarding gaseous boron with high-energy electrons in a mass spectrometer. Deduce the number of electrons in one B³⁺ ion.

c. Boron is present in compounds called borates.

i. Use the A_r values below to calculate the relative molecular mass of iron(III) borate, Fe(BO₂)₃. (A_r values: Fe = 55.8, B = 10.8, O = 16.0)
ii. The accurate relative atomic mass of iron, Fe, is 55.8. Explain why the accurate relative atomic mass is not a whole number.