59.0 mL of a 1.40 M solution is diluted to a total volume of 278 mL. A 139-mL portion of that solution is diluted by adding 129 mL of water. What is the final concentration? Assume the volumes are additive.
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To find the final concentration, we need to consider the total amount of solute (in this case, the solute is the substance that was dissolved in the original solution) before and after dilution.
First, let's calculate the amount of solute in the original solution:
Amount of solute before dilution = Volume of original solution × Concentration of original solution
Amount of solute before dilution = 59.0 mL × 1.40 M
Amount of solute before dilution = 82.6 moles
Next, let's calculate the new total volume after dilution:
Total volume after dilution = Original volume + Volume of water added
Total volume after dilution = 59.0 mL + 129 mL
Total volume after dilution = 188 mL
Now, we can calculate the final concentration using the following formula:
Final concentration = Amount of solute after dilution / Total volume after dilution
To find the amount of solute after dilution, we need to consider that the 139 mL portion is diluted with 129 mL of water. This means the amount of solute remains the same.
Amount of solute after dilution = Amount of solute before dilution = 82.6 moles
Now we can calculate the final concentration:
Final concentration = 82.6 moles / 188 mL
Final concentration ≈ 0.439 M
Therefore, the final concentration of the solution is approximately 0.439 M.