Question

Thomas has 235 grams of K2S in the chemistry lab. How many atoms of potassium (K) are in 235 grams of the compound?

Answer 1

The  number of atoms  of K that are in 235 g  of the compound  is

2.57 x10^24 atoms

 calculation

Step 1:  find the moles of K2S

= moles = mass/molar mass

=  235 g/110 g/mol= 2.136  moles

Step 2: multiply  2.136 moles  by no. of K atoms in K2S

= 2.136  x2 = 4.272 moles

Step 3: use the Avogadro's  law to determine number of K atoms

that is according to Avogadro's law  1 mole = 6.02 x 10^23  atoms

                                                            4.272 moles= ? atoms

by cross multiplication

= (4.272  moles x 6.02 x10^23 atoms)  / 1 mole = 2.57 x10^24 atoms