Question

Moles of Zn(NO3)2 in 151.50 g of this substance.Express your answer using four significant figures.

Number of molecules in 6×10⁻⁶ mol CH3CH2OH. Express your answer using four significant figures.

Number of N atoms in 0.550 mol NH3. Express your answer using three significant figures.

Answer 1

Molar mass of Zn(NO3)2 = 65.8 + (14+3*16)*2

=> 65.38 + 124

=> 189.38 gm/mol

Number of moles of Zn(NO3)2 = mass/molar mass = 151.50/189.38 = 0.7999 moles

b) One mole contains 6.023 * 10^(23) molecules of CH3CH2OH

Hence number of molecules in 6 * 10^(-6) mol CH3CH2OH

=> 6 * 10^(-6) * 6.023 * 10^(23)

=> 36.14 * 10^(17) molecules

c) One mole of NH3 contains one mole of nitrogen

0.550 moles of NH3 contains 0.550 moles of nitrogen

1 mole of nitrogen will contain 6.023 * 10^(23) atoms

Number of nitrogen atoms = 0.550 mol * 6.023 * 10^(23) atoms/mol = 3.31 * 10^(23) atoms