Question

How many molecules are in each of the following?

Part A 6.4 g H2O Express your answer using two significant figures.

412 g CBr4 Express your answer using three significant figures.

20.5 g O2 Express your answer using three significant figures

20.4 g C8H10 Express your answer using three significant figures.

Answer 1

1 mole of any sbstance having molecules = 1 vogadros number = 6.023 x 10²³ molecules

1) No.of moles of H2O = 6.4/18 = 0.3555 moles

no. of olecules in 0.3555 moles of water = 0.3555 x 6.023 x 10²³ = 2.14x 10²³ molecules of H2O

2) no.of moles of CBr4 = 412/331.63 = 1.24 moles

no. of molecules present in 1.24 moles of CBr4 = 1.24 x 6.023 x 10²³ = 7..48 x 10²³ molecules

3) no. of moles of O2 = 20.5/32 = 0.6406 moles

no. of molecules present in 0.6406 moles of O2 = 0.6406 x 6.023 x 10²³ = 3.86 x 10²³ molecules

4) no. of moles of C8H10 = 20.4/106.16 = 0.1921 moles

no. of molecules present in 0.1921 moles of O2 = 0.1921 x 6.023 x 10²³ = 1.16 x 10²³ molecules