What a standard solution is
Knowing how to calculate a concentration is one thing. Actually making a solution that has the concentration you calculated is another, and it is a practical skill with its own name.
Standard solution
A standard solution is a solution whose concentration is known very accurately.
Why the accuracy is the point
Chemistry experiments constantly need one. If a solution is used to measure something else — how much acid is in a sample, how much chloride is in a water supply — then any error in its own concentration passes straight into every result obtained with it. A standard solution is a ruler, and a ruler with the wrong markings is worse than no ruler.
The unit relationships it rests on
Preparing a solution of a very accurate concentration means moving between volume units without slipping, so these matter:
Learn these before you start
1 dm3 = 1 l (litre)
1 dm3 = 1000 cm3
1 dm3 = 1000 ml
1 cm3 = 1 ml
Accurate, not merely correct
Every solution has a concentration. What makes one standard is that the concentration is known accurately — which depends entirely on how carefully it was made, and that is what the next three pages are about.