Question

1. (1 pt) How many moles of K2S are 2.70 g K,S? 2. (1 pt) What is the mass of 4.26 g of K2S? 3. (1 pt) How many atoms of Cu are in 7.1 moles of Cu? 4. (1 pt) How many moles of C are in 5.80 x 10atoms of C? 5. (2 pts) How many atoms of Fe are in 81.4 g Fe? 6. (2 pts) What is the mass of 9.3 x 1024 atoms of Ar? 7. (2 pts) How many grams of silver, Ag, are in 2.65 moles of AgaCrO? How many grams of carbon are in 7.30 grams of acetaminophen, CHNO,? 9. (3 pts) How many oxygen atoms are in 3.22 grams of H SOA? lution is made from 11.30 g of KOH and enough water to make 500 mL of solution. What is 10. (3 pts) A solution is made from 11.30 g of KOL the molarity of the solution?

I need help solving these. I need to know the steps and calculations.

Answer 1

1) No of mol of compound (n)= weight / molecular weight

weight of K2S = 2.7 g

molecular weight of K2S = 110.3 g/mol

n = 2.7/110.3 = 0.0245 mol

2) mass of K2S = 4.26 G

3) no of atoms of Cu = n*N0     ( 1 mole = N0 = 6.023*10^23 atoms)

                     = 7.1*6.023*10^23

                     = 4.28*10^24 atoms

4) No of mole of C atoms = no of atoms/N0

                         = (5.8*10^21)/(6.023*10^23)

                         = 9.63*10^-3 mol

5) No of mole of Fe atoms = w/m.wt = 81.4/56 = 1.45 mol

   No of atoms of Fe = 1.45*6.023*10^23 = 8.735*10^23 atoms

6) Mass of Ar atoms = (no of atoms/No)*atomic mass of Ar

                    = ((9.3*10^24)/(6.023*10^23))*40

                    = 617.63 g

7) 1 mol Ag2Cr2O7 = 2 mol Ag

no of mol of Ag present = 2.65 mol

Mass of Ag present = n*At.wt

                   = 2.65*108

                   = 286.2 g