Answer: the final concentration is 0.656M
Explanation:
The <em>concentration</em> may be expressed in several ways. In this case, since the data talks about volume of the <em>solution</em>, the correct unit of the value 3.50 is M (capital M, and not m), so it is <em>3.50 M, which means 3.50 Molar</em>
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
<em>When it is said that the glucose solution is diluted to a volume of 400.0 ml</em>, 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.
