Question

2 .Determine moles and number of molecues. Calculate the following quantites.

A. The mass of hydrogen atoms in grams in .405 moles of sucrose C12H22O12

B. The moles in 196.5g of Zn(NO3)2

C. What is the mass in grams of 6.12 x 10^20 molecules of caffeine C8H10N4O2?

D. What is the molar mass of cholesterol if 0.00105 mol has a mass of 0.406g?

E. How many potassium atoms are in 28.6 grams of potassium nitirde, K3N?

F. How many grams are found in 6.8 x 10^24 atoms of Au?

G. How many grams are in 2.3 x 10^-4 moles of calcium phosphate Ca3(PO4)2?

Answer 1

1moles of sucrose C12H22O12 contains 22 moles of H

0.405 moles of sucrose C12H22O12 contains = 22*0.405 moles of H = 8.91 moles of H

mass of Hydrogen   = no of moles * atomic mass

                                 = 8.91 *1 = 8.91 g

B. The moles in 196.5g of Zn(NO3)2

no of moles of Zn(NO3)2    = W/G.M.Wt

                                              = 196.5/189.4   = 1.037 moles

C. What is the mass in grams of 6.12 x 10^20 molecules of caffeine C8H10N4O2?

    6.023 *10^23 molecules = 194g of C8H10N4O2

    6.12*10^20 molecules   = 194*6.12*10^20/6.023*10^23   = 0.197g of C8H10N4O2

D. What is the molar mass of cholesterol if 0.00105 mol has a mass of 0.406g

      molar mass = mass/no of moles

                           = 0.406/0.00105    = 386.7g/mole

E. How many potassium atoms are in 28.6 grams of potassium nitirde, K3N

         no of moles = W/G.M.Wt

                              = 28.6/131   = 0.218 moles

0.218 moles of K3N contains 3*0.218 moles of K

                                                 0.654 moles of K

no of K atoms   = no of moles * 6.023*10^23

                          = 0.654*6.023*10^23    = 3.94*10^23 atoms

F. How many grams are found in 6.8 x 10^24 atoms of Au?

      6.023*10^23 atoms of Au = 197 g of Au

      6.8*10^24 atoms of Au   = 197*6.8*10^24/6.023*10^23    = 2224g of Au

G. How many grams are in 2.3 x 10^-4 moles of calcium phosphate Ca3(PO4)2

mass of Ca3(PO4)2   = no of moles * gram molar mass

                                    = 2.3*10^-4 *310   = 0.0713 g of Ca3(PO4)2