Molarity is the number of moles of the molecule over the liters of solution. Thus, our first step is to find the number of moles of NaOH. To do this, we must find the molar mass of NaOH. Na is 22.99 g/mole, O is 16 g/mol, and H 1.008 g/mole, and NaOH would have a molar mass of 39.99 g/mol. Now, let's convert grams of NaOH into moles:
11.2 g * (1 mole/ 39.99 g)= 0.28 mole
A reminder that these moles need to be placed over the liters of solution. Let us convert the mL into L:
225 mL *(1 L/1000 mL)=0.225 L
Now that we have moles and liters we just need to divide the two
M(molarity)= 0.28 mol / 0.225 =1.24 M
I hope this was helpful and helps you approach similar problems like these
