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# The solubility curve of $KN{O_3}$ in water is shown below. The amount of $KN{O_3}$ that dissolves in $50g$ of water at $40^\circ C$ is closest toA. $100g$B. $150g$C. $200g$D. $50g$

Last updated date: 09th Sep 2024
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Hint:As we need to find out the solubility at $40^\circ C$, we can draw a line from the point $40^\circ C$ in the $x - axis$ to meet the curve. From this meeting point, we can draw a horizontal line to the $y - axis$ to find the solubility per $100g$. Dividing this value by two will give us our answer.
Since the temperature is given in the $x - axis$, we have to first draw a vertical line from the point $40^\circ C$ and extend it upwards till it meets the solubility curve. From the point of intersection of this line and the solubility curve, we should draw a horizontal line and extend it till it meets the $y - axis$. The point of intersection of this horizontal line and the $y - axis$ will give us the value on the $y - axis$ corresponding to the value on the $x - axis$. Since the intersection point is closest to $200g$, we can say that at a temperature of $40^\circ C$, the solubility of potassium nitrate ($KN{O_3}$) per $100g$ of water is $200g$. But we are required to find the quantity that dissolves in $50g$ of water at $40^\circ C$ , and not $100g$. Therefore, to get the answer per $50g$, we just have to divide the answer which we got per $100g$ by two. Hence,
Amount of potassium nitrate that dissolves in $50g$ of water at $40^\circ C$ $= \dfrac{{200}}{2} = 100g$