Question

Calculate the following.
(a) Mass of one mole of calcium.
(b) Number of sodium atom in its 25 g sample. ​

Answer 1

(a) The Molar Mass of Calcium

The number under the symbol for calcium, Ca, tells you the molar mass of the element.

This is the number of grams in 1 mole of calcium.

The mass of 1 mole of calcium is 40.078 grams.

(b) Na or sodium has an atomic mass of 22.98977

So, if we divide the mass of our sample 11.5g by this number we get 11.5 / 22.98977

= 0.50022249 moles of sodium. 6.023× 0.50022249 × 10^23 atoms

= 3.0128 × 10^23 atoms.

Therefore 25g of sodium= 25×(3.0128 × 10^23) atoms.

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Answer 2

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