How many grams of NaOh are needed to prepare 0.5l of a 4m solution?
To calculate the number of grams of NaOH needed to prepare a 0.5 L solution with a concentration of 4 M, you'll need to use the formula:
grams = moles x molar mass
First, let's find the number of moles needed. The concentration is given as 4 M, which means 4 moles of NaOH are dissolved in 1 liter (1000 mL) of solution.
moles = concentration x volume in liters
= 4 M x 0.5 L
= 2 moles
Now, we can calculate the molar mass of NaOH, which can be obtained from the periodic table. The molar mass of Na is approximately 23 g/mol, and the molar mass of O is approximately 16 g/mol. Hydrogen (H) is not explicitly mentioned in your question, but we can assume it's present since NaOH is a strong base. The molar mass of H is approximately 1 g/mol.
So, molar mass of NaOH = (23 g/mol) + (16 g/mol) + (1 g/mol)
= 40 g/mol
Lastly, we multiply the moles by the molar mass to find the grams of NaOH needed:
grams = moles x molar mass
= 2 moles x 40 g/mol
= 80 grams
Therefore, you will need 80 grams of NaOH to prepare 0.5 L of a 4 M solution.