On dispose de 200 mL d'une solution de chlorure de potassium (KCl) de concentration 0,4 M. Quel

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On dispose de 200 mL d'une solution de chlorure de...

On dispose de $200 \mathrm{~mL}$ d'une solution de chlorure de potassium $(\mathrm{KCl})$ de concentration $0,4 \mathrm{M}$. Quelle est la concentration molaire en $\mathrm{KCl}$ des solutions obtenues en y ajoutant : a) $500 \mathrm{~mL}$ d'eau b) $250 \mathrm{~mL}$ de la même solution c) $200 \mathrm{~mL}$ d'une solution de bromure de sodium $\mathrm{NaBr} 0,1 \mathrm{M}$ d) $100 \mathrm{~mL}$ d'une solution de $\mathrm{KCl} 0,1 \mathrm{M}$ e) $1,49 \mathrm{~g}$ de $\mathrm{KCl}$ solide (dont le volume est supposé négligeable par rapport à celui de la solution).

On dispose de $200 \mathrm{~mL}$ d'une solution de chlorure de potassium $(\mathrm{KCl})$ de concentration $0,4 \mathrm{M}$. Quelle est la concentration molaire en $\mathrm{KCl}$ des solutions obtenues en y ajoutant :
a) $500 \mathrm{~mL}$ d'eau
b) $250 \mathrm{~mL}$ de la même solution
c) $200 \mathrm{~mL}$ d'une solution de bromure de sodium $\mathrm{NaBr} 0,1 \mathrm{M}$
d) $100 \mathrm{~mL}$ d'une solution de $\mathrm{KCl} 0,1 \mathrm{M}$
e) $1,49 \mathrm{~g}$ de $\mathrm{KCl}$ solide (dont le volume est supposé négligeable par rapport à celui de la solution).

Key Concepts

Molarity

Molarity is a measure of concentration expressed as the number of moles of solute per liter of solution. It is a key concept for quantifying how concentrated a solution is and is used in a wide variety of chemical calculations, including reaction stoichiometry and dilution procedures.

Dilution Principle

The dilution principle states that when additional solvent is added to a solution, the total number of solute moles remains constant while the volume increases, leading to a reduction in concentration. This is typically represented by the formula M1V1 = M2V2, assuming no chemical reaction occurs and only dilution takes place.

Conservation of Solute Moles

Conservation of solute moles is the concept that when solutions are mixed or diluted without any chemical reaction, the total amount of solute (in moles) remains unchanged. This principle is essential for calculating new concentrations when volumes are altered or different solutions are combined.

Mixing Solutions with Different Concentrations

When combining two solutions with the same solute but different concentrations, the total number of moles from each solution must be summed and then divided by the new total volume to determine the overall concentration. This concept is crucial for accurately determining the properties of mixed solutions.

Adding Solid Solutes to a Solution

Adding a solid solute to an existing solution involves calculating the number of moles of the solid based on its mass and molar mass, then determining the new concentration by adding these moles to the original moles present in the solution. This process is fundamental when adjusting concentrations through supplementation of additional solute.

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