Which sample has the fewest number of atoms

Question

A. 24.3g of Magnesium

B. 9.0g of Beryllium

C. 5.1g of Lithium

D. 12.0g of Carbon

Answer 1

Hi Libertie D.,

I won't tell you the answer, but show you what to do to find it out yourself.

Take a periodic table of the elements.

For each of your answer choices, divide the specified mass of that sample by the atomic weight of that element. So for 24.3 g Mg, divide by 24.305 (g/mole). Write down the answer, and the units! (moles).

Do this for each answer choice, then compare the calculated values for moles of each. The lowest value takes it! (Hint: one of them is decidedly lower than the rest; the rest cluster around 1.0 moles)

-- Cheers, Mr. d.

Answer 2

There will be 6.02x10²³ atoms in 1 mole of any of these elements. So, find the number of moles of each, and whichever is the lowest number of moles will be the fewest number of atoms.

A. 24.3 g Mg x 1 mol Mg/24.3 g = 1 mole Mg

B. 9.0 g Be x 1 mol Be/9.01 g = 1 mole Be

C. 5.1 g Li x 1 mol Li/6.94 g = 0.73 mole Li

D. 12.0 g C x 1 mol C/12.0 g = 1 mole C

Therefore, (C) 5.1 g of lithium will have the fewest number of atoms.