To use Avogadro\'s number to convert between microscopic units of atoms and mole

Question

To use Avogadro's number to convert between microscopic units of atoms and molecules to the macroscopic world of chemical experiments. A mole is a unit of matter that represents a known number of particles that is large enough to be weighed on a laboratory balance. One mole of substance contains 6.022 Times 10^23 formula units, as shown in the following unit factor: 6.022 Times 10^23 formula units/1 mol substance The value 6.022 Times 10^23 is called Avogadro's number. The term formula unit is a generic phrase that can mean a molecule, atom, ion, or whatever is represented by the chemical formula. For example, a mole of He contains 6.022 Times 10^23 helium atoms. A mole of N_2 contains 6.022 Times 10^23 diatomic N2 molecules but double that number of nitrogen atoms. Calculate the mass of 1.00 Times 10^24 (a septillion) molecules of water. Express the answer numerically in grams. This value is close to the mass of a fluid ounce of water (29.6 mL). Now you know that one fluid ounce of water contains approximately 10^24 (a trillion trillion) molecules. The fuel used in many disposable lighters is liquid butane, C_4H_10. How many carbon atoms are in 3.50 g of butane? Express your answer numerically in atoms.

Explanation / Answer

Molar mass of butane = 4*12 + 10*1 = 58 g
mass = 3.50 g
number of moles of butane = mass/molar mass
= 3.50/58 mol
= 0.0603
Number of moles of C = 4*0.0603 mol = 0.2414 mol
Number of atom = 0.2414*6.022*10^23 = 1.45*10^23 atoms

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