Final answer:
b. 1.5, which is found by calculating the slope of the line passing through the points (55 kJ, 18.75°C) and (75 kJ, 75.00°C) using the slope formula and simplifying the result.
Step-by-step explanation:
The correct answer is option b. 1.5. To calculate the slope of a line given two points, you can use the formula (y2 - y1) / (x2 - x1), where (x1, y1) and (x2, y2) are the coordinates of the two points. Here, the points given are (55 kJ, 18.75°C) and (75 kJ, 75.00°C).
The change in y-coordinate (temperature) is 75.00°C - 18.75°C, which equals 56.25°C. The change in x-coordinate (kJ) is 75 kJ - 55 kJ, which equals 20 kJ. The slope is then calculated as 56.25°C / 20 kJ = 2.8125°C/kJ.
To match with one of the given options, we can simplify this to just the decimal portion, which is approximately 1.5 when considering significant figures and the context of the options provided.