To determine the mass of a substance, you need to know its molar mass. The molar mass of sodium hydroxide (NaOH) can be calculated by summing the atomic masses of its constituent elements.
The atomic masses of sodium (Na), oxygen (O), and hydrogen (H) are approximately:
Na: 22.99 g/mol O: 16.00 g/mol H: 1.01 g/mol
To find the molar mass of NaOH, you add the atomic masses of each element:
Na: 1 atom x 22.99 g/mol = 22.99 g/mol O: 1 atom x 16.00 g/mol = 16.00 g/mol H: 1 atom x 1.01 g/mol = 1.01 g/mol
Summing these values, we get:
Molar mass of NaOH = 22.99 g/mol + 16.00 g/mol + 1.01 g/mol = 40.00 g/mol
Now, to calculate the mass of 2.5 moles of NaOH, we multiply the molar mass by the number of moles:
Mass = 2.5 moles x 40.00 g/mol = 100.00 g
Therefore, the mass of 2.5 moles of NaOH is 100.00 grams.