College

**Chemistry Semester-1 Final: Written Final (Graphing and Density)**

1. Potassium nitrate [tex]\(\left( \text{KNO}_3\right)\)[/tex] is a chemical compound with many uses, including as a food preservative and fertilizer. It is an ionic compound and dissolves in water. The amount of [tex]\(\text{KNO}_3\)[/tex] that dissolves depends on the temperature of water.

**Task:** Graph the data below, which shows the solubility of potassium nitrate at varying temperatures of water. Make sure that the independent variable (temperature) corresponds to the [tex]\(X\)[/tex] axis, and the dependent variable (solubility) corresponds to the [tex]\(Y\)[/tex] axis. Ensure to appropriately scale and label your axes.

[tex]
\[
\begin{array}{|c|c|c|c|c|c|c|c|c|c|c|c|}
\hline
\text{Temp (°C)} & 0 & 10 & 20 & 30 & 40 & 50 & 60 & 70 & 80 & 90 & 100 \\
\hline
\text{Solubility (g/100 mL)} & 13 & 21 & 32 & 46 & 64 & 86 & 110 & 138 & 169 & 202 & 246 \\
\hline
\end{array}
\]
[/tex]

Answer :

To solve this problem, you need to graph the given data which shows the solubility of potassium nitrate (KNO₃) at various temperatures.

Here’s how you can create the graph step-by-step:

1. Set up the Graph Axes:
- Independent Variable (X-axis): This will be the temperature in degrees Celsius (°C). This is because we are examining how the solubility changes with temperature changes.
- Dependent Variable (Y-axis): This will be the solubility of KNO₃ in grams per 100 mL of water. This is what changes in response to different temperatures.

2. Label the Axes:
- Label the X-axis as "Temperature (°C)"
- Label the Y-axis as "Solubility (g/100 mL)"

3. Scale the Axes:
- For the X-axis (temperature), you can use intervals that match the data points provided, such as 0°C, 10°C, 20°C, …, 100°C.
- For the Y-axis (solubility), start from 0 and choose an appropriate scale that accommodates the highest value (246 g/100 mL). You might use intervals of 20 up to 260 for clarity.

4. Plot the Data Points:
- Plot each data point on the graph based on the values provided:
- At 0°C, plot a point at 13 g/100 mL.
- At 10°C, plot a point at 21 g/100 mL.
- At 20°C, plot a point at 32 g/100 mL.
- At 30°C, plot a point at 46 g/100 mL.
- At 40°C, plot a point at 64 g/100 mL.
- At 50°C, plot a point at 86 g/100 mL.
- At 60°C, plot a point at 110 g/100 mL.
- At 70°C, plot a point at 138 g/100 mL.
- At 80°C, plot a point at 169 g/100 mL.
- At 90°C, plot a point at 202 g/100 mL.
- At 100°C, plot a point at 246 g/100 mL.

5. Draw the Graph:
- Connect the plotted points with a smooth curve to show how solubility changes with temperature. Typically, this is a line or curve that best represents the trend in the data.

6. Review the Graph:
- Check that all points are correctly plotted and that the axes are properly labeled and scaled.
- Ensure the curve reflects the overall trend of increasing solubility with increasing temperature.

By following these steps, you’ll have created a graph that visually represents how the solubility of potassium nitrate in water changes as the temperature increases. This graph can be used to analyze and predict the solubility at various temperatures.