Answer: the final concentration is 0.656M
Step-by-step explanation:
The concentration may be expressed in several ways. In this case, since the data talks about volume of the solution, the correct unit of the value 3.50 is M (capital M, and not m), so it is 3.50 M, which means 3.50 Molar
Hence, we are dealing with molarity.
The equation for molarity, M, is:
- M = number of moles of solute / volume of solution in liters
Wnen you solve for the number of moles of solute, you get:
- number of moles of solute = M × volume in liters of the solution
When it is said that the glucose solution is diluted to a volume of 400.0 ml, means than only solvent was added. That implies, that the number of moles of solute of the final (diluted) solution is the same number of moles of the 3.50 M glucose solution.
That permits you to wite theses equations:
- # moles of glucose in 3.50 M solution, n₁
n₁ = 3.50 M × 75.0 ml × 1 liter/1000 ml
- # moles of glucose in the diluted solution, n₂
n₂ = C × 400.0ml × 1 liter / 1000 ml
⇒ 3.50 M × 75.0 ml × 1 liter/1000 ml = C × 400.0ml × 1 liter / 1000 ml
- Solve for the unknown concentration, C:
C = 3.50 M × 75.0 / 400.0 = 0.656M
The answer is expressed with three significant digits, because 75.0 ml and 3.50 M are expressed with three significant digits.