What volume in milliliters of a 10% (m/v) NaOH solution contains 45 g NaOH?

While preparing solutions, we often use terms such as m/m or w/w, v/v, m/v, etc. m/v stands for mass by volume, that is, solute is measured in terms of mass, while the solvent is measured in terms of volume. 

A 100% m/v solution (prepared in water) contains 1 g per ml or 1 kg per l. This is because the density of water is about 1 g per ml or 1 kg per l. 

A 10% m/v solution would then mean 1 g per 10 ml.

Using unitary method, 1 g is in 10 ml (for 10% solution).

Then, 45 g would be in 10 ml x 45 g / 1 g = 450 ml.

Thus, 450 ml of a 10% m/v solution of sodium hydroxide (NaOH) will contain 45 g NaOH.

Hope this helps.