0.2 M ammonium hydroxide?

Dissolve, 7g of Ammonium Hydroxide in 1 litre of water..............

1 M of ammonium hydroxide will have 35 g of it in 1 litre of water (As 1 mole of ammonium hydroxide will be of 35g)

Now, use unitary method to determine for .2 M

you must weight 0.2 mole of NH4OH, and then add this quantity to a volume of distilled water enough to make 1 litre of dissolution. (Take into account that the hydroxide has certain volume, so the water added should be less that 1 litre).Use a second empty flask with marked volume at 1l., and after dissolve the hydroxide in a small amount of water and pour it inside the marked flask. After this, stir while filling the flask with water up to the mark.

0.2 mole hydroxide are approx. 35 * 0.2 = 7 g NH4OH

M means concentration,which is usually taken in moles/dm^3

1mole of any gas occupies 24dm^3 at room temperature.

0.2moles will have 4.8dm^3

Simply take Ammonia Gas (NH3) of 4.8dm^3 and dissolve it in 1dm^3 of distilled water,and you will have a solution of 0.2M NH4OH