Question

Sodium hydroxide, NaOH, is a strong base that is used in industrial synthesis and processes such as making paper. What is the mass of 2.60 ×1022 molecules of NaOH (Molar mass = 40.0 g/mol)?

Answer 1

  The  mass of 2.60 x10^22  molecules of NaOH  is   1.728   grams

calculation
 mass = moles  x molar mass
   molar mass = 40 g/mol

mole   is calculated   using the Avogadro   law
that is  1 mole =   6.02 x10^23 molecules
              ?        =  2.60  x10 ^ 22  molecules

by   cross   multiplication

 (1 mole x  2.60  x10^22) /  6.02 x0^23  =  0.0432  moles

mass   is therefore= 0.0432  mole x  40 g/mol = 1.728 grams

Answer 2

Answer : Mass would be = 1.859 g for NaOH

Explanation :  We have got $2.88 X 10^{22}$ molecules of NaOH,

so we get,

$\frac{2.88 X 10^{22} moles of NaOH }{6.022 X 10^{23}/mol } X 40.0$ g of NaOH/mol

On solving we get, answer as 1.859 g

Hence the g of NaOH will be 1.86.