Consider the HF solution with the concentration of 5% (w/v). Calculate its concentration in the molarity. Use four significant figures in your answer

5% w/v means 5g HF in 100 mL solution.

mols HF = grams HF/molar mass HF
Then M = mols/0.1L = ?
Note: 100 mL solution is 0.1 L solution.