How many grams of koh are needed to prepare 400 ml of 0.350 m koh solution?

It is to be assumed that the unit of the given concentration is in molarity. To determine the number of moles given molarity and volume, we use the equation,

    m = (M)(V)

volume should be in liters. Substituting the known values,
  
     m = (0.350)(0.40 L)   
     m = 0.14 mols

Then, multiply the number of moles by the molar mass of KOH which is equal to 56.1056 g/mol.

     mass  = (0.14 mols)(56.1056 g/mol)
     mass = 7.855 grams

7.855 grams