How many grams of NaCl are needed to prepare 200. grams of a 10% salt
solution?
10% of 200. grams = 20.0 grams of saltYou could also solve the problem using the above formula and solving for
the unknown quantity.
TIP
Know how to calculate molarity (M).The next two expressions depend on the fact that, if the formula mass of a
substance is expressed in grams, it is called a gram-formula mass (gfm), molar
mass, or 1 mole. Gram-molecular mass can be used in place of gram-formula
mass when the substance is really of molecular composition, and not ionic like
NaCl or NaOH. The definitions and examples are:
- MOLARITY (abbreviated M) is defined as the number of moles of a
substance dissolved in 1 liter of solution.
A 1 molar H 2 SO 4 solution has 98. grams of H 2 SO 4 (its molar mass) in 1
liter of the solution.This can be expressed as a formula:If the molarity (M) and the volume of a solution are known, the mass of the
solute can be determined. First, use the above equation and solve for the number
of moles of solute. Then, multiply this number by the molar mass.
Example
How many grams of NaOH are dissolved in 200. milliliters of solution if its
concentration is 1.50 M?