Question

What mass of HCL is contained in 645 mL of 0.266 M solution?

Answer 1

is this the correct answer

6.27 g HCl

Answer 2

You have not shown us how you got that answer.
Method you could use:
moles = (liters)(molarity)
mol. HCl = (0.645L)(0.266mol/L) = _____ mol HCl
(____ mol HCl)(35.453g/mole) = ______?

Answer 3

6.08 moles of HCL