Question

a pure solid sample of substance x is put into an evacuated flask. the flask is heated at a steady rate and the temperature recorded as time passes. here is a graph of the results: use this graph to answer the following questions: what is the boiling point of x? ______°c what phase (physical state) of x would you expect to find in the flask after 16 kj/mol of heat has been added? (check all that apply) ☐ solid ☐ liquid ☐ gas

Explanation:

First Question: Boiling Point of X

Step1: Identify Boiling Point Region

Boiling point is where temperature stays constant during heating (liquid to gas phase change). On the graph, find the horizontal segment corresponding to boiling.

Step2: Read Temperature at Boiling

From the graph, the horizontal segment for boiling (liquid - gas transition) occurs at \( 150^\circ \text{C} \) (checking the temperature axis for the horizontal part related to boiling).

Step1: Analyze Heat vs Phase

• First horizontal segment: melting (solid - liquid, heat 0 - ~8 kJ/mol? Wait, looking at the graph:
• Initial: solid (heat 0, temp low).
• First horizontal: melting (solid to liquid, heat up to ~10 kJ/mol? Wait, the heat added axis: 0,10,20,30,40,50. The first horizontal (melting) is around 0 - 10 kJ/mol? Then liquid heating (temp rises) until boiling (around 30 - 45 kJ/mol? Wait, no, the graph:
• Let's parse the graph:
• Heat 0 - ~10 kJ/mol: melting (solid to liquid, temp constant ~70 - 80? No, the temp axis: 50,70,90,110,130,150,170. Wait, the first horizontal (melting) is at temp ~70 - 80? Then liquid (heat 10 - 30 kJ/mol, temp rises to 150? Wait, no, the second horizontal is boiling (liquid to gas) at 150, heat 30 - 45? Wait, the heat added is 16 kJ/mol.
• After melting (which is up to ~10 kJ/mol? Wait, maybe the first horizontal (melting) is from heat 0 to ~10 kJ/mol (temp constant), then liquid phase (heat 10 - 30 kJ/mol, temp rises), then boiling (heat 30 - 45 kJ/mol, temp constant at 150), then gas (heat >45, temp rises).
• So 16 kJ/mol is after melting (so liquid phase, since 16 is between 10 and 30, where temp is rising (liquid heating), so phase is liquid.

Step2: Confirm Phase

At 16 kJ/mol, heat is above melting (solid - liquid transition) and below boiling (liquid - gas transition), so the substance is in liquid phase.

Answer:

\( 150 \)

Second Question: Phase after 16 kJ/mol Heat