General plan for solving problems

A scheme summarizing the three-step problems in this module is shown below. Using this scheme,
either the mass or the concentration and volume of a known substance can be related to
the mass or the concentration or volume of an unknown substance
if the two substances are involved in a reaction for which the balanced equation is known. 

First  Calculate amount in moles of unknown substance	n = c × V ( × (   = mol) from known volume and concentration n = m (g ÷ g mol–1 = mol) M from known mass and formula of a pure substance
Then Relate calculated n(known) to n(unknown) using any pair from	For aA + bB → cC + dD n(A) = n(B) = n(C) = n(D) a b c d A, B, C and D substances; a, b, c, d coefficients
Then From calculate the desired quantity from n(unknown) using	c = n/V if volume is known and concentration is unknown V = n/c if volume is unknown and concentration is known m = n × M if the formula is known and mass is unknown