How many moles of tin atoms are in a pure tin cup with a mass of 30.4 g ?

ANSWER: 0.331 moles of tin

Explanation: in my working * means multiply and ^ means to the power of.

Ok BASICALLY if you have 6.02*10^23 of something you have yourself 1 mole of things. The atomic weight in the left hand corner of each element in the periodic table gives you the MOLAR MASS, which is the mass of 1 mole of that element. For example, Carbon has a molar mass of 12.011, this means it has 12.011 grams every 1 mole of carbon [C] (12.011 g/mol)

So now, how many moles are in 39.3 grams of tin? Very easy. You will find that in chemistry classes students are taught a basic formula to find the number of moles, which is:

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Number of moles = Mass given / Molar mass

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So in order to answer this question and find out the NUMBER OF MOLES, we need to find the MASS GIVEN - this is simply the mass given to you in the question, which is 39.3 grams of tin. We also need to know the MOLAR MASS, which is found in the left hand corner of the element. For tin [Sn] the molar mass is 118.710.

Sub both these into the formula to get:

Number of moles = 39.3 / 118.710

Number of moles = 0.331058883

We are not finished - remember to round of the lowest amount of significant figures found in the working of the question. In the working out, which was (39.3 / 118.71) the 39.3 has 3 significant figures and the 118.70 has 5 significant figures. ALWAYS TAKE THE LOWEST AMOUNT FOUND. The lowest amount is 3, so we must round this answer to 3 significant figures.

It will be: 0.331

Therefore, 0.331 moles of tin atoms are in a pure tin cup with a mass of 39.3.

Hope i helped and good luck!