Which of the following has the smallest mass?

Question

a. 1.75 x 1023 atoms of iron

b. 13.5 grams of copper

c. 0.38 moles of chromium

d. 0.50 ounces of zinc

Answer 1

Hi Anna! To solve this, we have to convert all of the answers to grams. For answer choice a, we need to divide the number of atoms we're given (1.75 x 10²³) by Avagadro's number (6.02 x 10²³) to find the number of moles of iron we have. When we do this, we find out we have 0.29 moles of iron. Multiplying this by iron's atomic mass on the periodic table (55.845 g/mol), we find 16.19 grams of iron! We luck out with answer choice b, because it's already in grams! Answer choice c is similar to answer choice a, but we already have our moles, so we just multiply it by chromium's mass from the periodic table (51.996 g/mol), which gives us 19.758 grams. For answer choice d, we need to know the conversion for ounces to grams, which is one ounce = 28.35 grams. Since we only have a half-ounce, that comes out to 14.17 grams. Now we can see that in terms of mass, answer b is the smallest! Hope this helps!!

Answer 2

We need to convert all of the elements to the same unit so we can compare them. For this, let’s convert all of them to grams.

a. 1.75 * 10²³ atoms of iron * (1 mol iron/6.022 * 10²³ atoms iron) * (55.85 g/1 mol iron) = 16.23 g of iron

b. 13.25 g of copper is already in grams

c. 0.38 moles of chromium * (52 g/mol chromium) = 19.76 g of chromium

d. 0.50 ounces of zinc * (28.35 g/1 oz) = 14.18 g of zinc

Therefore, copper is the smallest amount