How do I Convert 7.75 × 10²¹ atoms of carbon to Grams

Question

with appropriate significant figures

Answer 1

Hi there!

So any time you see atoms of something...you think should of avogardo's number.

So we start with  7.75 × 10²¹ atoms of carbon and we want grams

so what conversion factor can we use to get from atoms to grams?

We take 7.75 * 10²¹ atoms of carbon X 1 mole carbon x 12.011 grams of carbon

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6.022* 10²³ atoms of carbon 1 mole of carbon

we then multiple the numbers and make sure our units cancel out so that we end only with grams of carbon! so we should get 0.154575307 as the number our calculator spits out. Because 7.75 has only three significant figures, so should your answer. The significant figures start occurring from the first non-zero digit from the decimal point. So, our answer would be 0.155 grams of Carbon

Answer 2

We want to start first by converting this number to moles of carbon using Avogadro's number (6.02 x 10^23 atoms per mol). Once you have mols of Carbon, convert to grams using the molar mass number of Carbon