Picture attatched: The following cooling curve was obtained for a solution of an
ID: 782500 • Letter: P
Question
Picture attatched:
The following cooling curve was obtained for a solution of an unknown compound mixed with a solvent that freezes at 76.81 degree C. When the "Analyze" button was clicked in this experiment two of the three linear lines on the cooling curve were calculated. (All three equations for the linear lines are shown on this graph.) From the equations of the two appropriate lines, the time at the point of intersect was found and this time used with one of the equations to find the temperature at the intersection point or the freezing point of the solution. Select the appropriate two lines and find the freezing point of the solution.Explanation / Answer
When a liquid is cooled and it reaches its freezing point. It starts to freeze slowly. Over a periiod of time until it completely freezes, the temperature of the substance stays the same..Then after the freezing is complete, the temperature drops further. As we want the freezing point, The appropriate two lines will be T = 93.29 -0.11t and T = 73.76 - 0.0008t. This is the point where the liquid first starts to freeze. This is because the point of intersection of above lines T = 73.76 - 0.0008t and T = 109.57 - 0.100t gives us the point when the temperature starts to drop further down after the freezing is complete. So solving the appropriate two lines T = 93.29 -0.11t and T = 73.76 - 0.0008t we get , T = 73.62 C and t= 178.85 seconds