Question

1. Moles of Zn(NO3)2 in 111.50 g of this substance.

Express your answer using four significant figures.

n =        mol  

2. Number of molecules in 4×10⁻⁶ mol CH3CH2OH.

Express your answer using four significant figures.

N =          molecules 

3. Number of N atoms in 0.450 mol NH3.

Express your answer using three significant figures.

N =          atoms

Answer 1

1.

mass of Zn(NO3)2 = 111.50 grams

molar mass of Zn(NO3)2 = 189.36 gram/mole

Number of moles = mass of substance/molar mass = 111.50/189.36 = 0.5888 moles

number of moles of Zn(NO3)2=0.5888 moles.

2. number of moles of CH3CH2OH= 4x10^-6 moles

1mole of CH3CH2OH contains Avagadro nu,mber of molecules

1 mole of CH3CH2OH contains = 6.023 x 10^23 molecules

4x10^-6 moles of CH3CH2OH contains = ?

                                                         = 4 x10^-6 x 6.023 x 10^23 = 24.092 x10^17 molecules

Number of molecules of CH3CH2OH= 2.409 x 10^18 molecules.

3.

number of moles of NH3 =0.450 moles

1 mole of NH3 conatins 1 mole of Nitrogen

1 mole of Nitrogen contains Avagadro number of atoms of Nitrogen

1 mole of NH3 contains = Avagadro number of Nitrogen atoms

1 mole of NH3 contains = 6.023 x 10^23 atoms of Nitrogen

0.450 moles of NH3 conatins = ?

                                               =0.450 x 6.023 x 10^23 = 2.71035 x 10^23atoms of Nitrogen

number of nitrogen atoms = 2.71 x 10^23 atoms.