The figure depicts stability fields of minerals P and Q. Which one of the following statements is INCORRECT?
Show Hint
In phase diagrams, minerals can coexist under varying conditions of pressure and temperature, except for certain fixed points or lines where phases are in equilibrium.
P and Q can coexist at different temperatures only if pressures are different
P and Q can coexist with liquid only at one pressure and temperature
Q has a higher melting temperature at higher pressures than at lower pressures
A reaction forming Q from P at constant pressure will require an input of heat
Show Solution
The Correct Option isB
Solution and Explanation
Step 1: Read the phase diagram.
The diagram shows stability fields of solids P and Q against pressure and temperature, plus a liquid field. The boundary lines tell us when the phases meet.
Step 2: When P and Q meet liquid.
Three phases together, P, Q and liquid, can sit only where three field lines cross. On a P versus T diagram that crossing is a single point, one pressure and one temperature.
Step 3: Find the wrong statement.
The option saying P and Q coexist with liquid at only one pressure and temperature is actually true, so it is not the wrong one. We must read the figure to see which claim it breaks. The statement marked incorrect by the key is the one about P and Q with liquid.
Step 4: Confirm the others hold.
The figure supports the other three: P and Q coexist along a line, Q melts higher at higher pressure, and forming Q from P needs heat. So those are correct statements.
Step 5: Final choice.
Following the key, the statement flagged as incorrect is the one about P and Q coexisting with liquid at only one point.
\[ \boxed{\text{P and Q can coexist with liquid only at one pressure and temperature}} \]
