Potassium iodide (KI) has a molecular mass of 166 grams / (mole) . What is the molarity of a KI solution with a concentration of 83 grams/liter
The Correct Answer and Explanation is:
To find the molarity of a potassium iodide (KI) solution with a concentration of 83 grams per liter, we use the following formula:Molarity (M)=mass of solute (g)molar mass (g/mol)×volume of solution (L)\text{Molarity (M)} = \frac{\text{mass of solute (g)}}{\text{molar mass (g/mol)} \times \text{volume of solution (L)}}Molarity (M)=molar mass (g/mol)×volume of solution (L)mass of solute (g)
Given:
- Mass of KI = 83 g
- Molar mass of KI = 166 g/mol
- Volume of solution = 1 L (since the concentration is per liter)
Now, calculate the molarity:Molarity=83 g166 g/mol×1 L=0.5 mol/L\text{Molarity} = \frac{83 \text{ g}}{166 \text{ g/mol} \times 1 \text{ L}} = 0.5 \text{ mol/L}Molarity=166 g/mol×1 L83 g=0.5 mol/L
Answer: The molarity of the KI solution is 0.5 M.
Explanation
Molarity is one of the most common ways to express the concentration of a solution in chemistry. It is defined as the number of moles of solute per liter of solution. The formula is straightforward:M=nVM = \frac{n}{V}M=Vn
Where n is the number of moles of solute, and V is the volume of the solution in liters.
To find the number of moles, we divide the mass of the solute by its molar mass. Potassium iodide (KI) has a molar mass of 166 g/mol, meaning 1 mole of KI weighs 166 grams. If we have 83 grams of KI, we divide this by 166 g/mol to find the number of moles:83166=0.5 moles\frac{83}{166} = 0.5 \text{ moles}16683=0.5 moles
Since the solution has 83 grams of KI per 1 liter of solution, and we’ve determined that 83 grams equals 0.5 moles, the molarity is:0.5 moles per liter=0.5 M0.5 \text{ moles per liter} = 0.5 \text{ M}0.5 moles per liter=0.5 M
This tells us that every liter of this KI solution contains half a mole of KI. Understanding molarity is essential in chemical reactions and solution chemistry, as it helps chemists know how much of a substance is available for a reaction. Whether preparing buffers, titrations, or medications, accurately calculating molarity ensures predictable results.
