using the phase diagram for co₂, what phase is carbon dioxide in at -20°c and 1 atm pressure?\na. it is in…

Brief Explanations:

To determine the phase of ( \text{CO}_2 ) at (-20^\circ\text{C}) and 1 atm, we analyze the phase diagram. First, identify the coordinates: temperature (-20^\circ\text{C}) (x - axis) and pressure 1 atm (y - axis). Then, locate this point on the diagram. The phase regions are labeled: solid (left - lower), liquid (middle), gas (right - lower). At 1 atm (which is approximately 1.013 bar, close to 1 atm on the y - axis) and (-20^\circ\text{C}), the point lies in the gas region? Wait, no, wait. Wait, the phase diagram for ( \text{CO}_2 ): actually, at 1 atm, the sublimation point of ( \text{CO}_2 ) is around (-78.5^\circ\text{C}). Wait, maybe I misread the diagram in the question. Wait, the diagram in the question: let's check the axes. Temperature on x - axis (from, say, - 100 to 50? The labels: - 10, - 8, - 6, - 4, - 2, 0, 2? Wait, maybe the diagram is a simplified one. Wait, the options: let's re - evaluate. Wait, 1 atm pressure. Let's recall: at 1 atm, ( \text{CO}_2 ) sublimes (goes from solid to gas) at (-78.5^\circ\text{C}). So at (-20^\circ\text{C}) and 1 atm, since (-20^\circ\text{C}) is higher than (-78.5^\circ\text{C}) at 1 atm, ( \text{CO}_2 ) should be a gas? Wait, no, wait: no, wait, the phase diagram for ( \text{CO}_2 ) has a triple point at 5.11 atm and (-56.6^\circ\text{C}). So at pressures below the triple point pressure (5.11 atm), the phases are solid and gas (sublimation) or gas and... Wait, at 1 atm (below triple point pressure), the phase transition between solid and gas is sublimation. So at (-20^\circ\text{C}) and 1 atm, since (-20^\circ\text{C}) is above the sublimation temperature at 1 atm ((-78.5^\circ\text{C})), ( \text{CO}_2 ) is in the gas phase? But wait, maybe the diagram in the question is different. Wait, the diagram in the question: the pressure axis is in atm (0 - 20 atm), temperature in (^\circ\text{C}) ( - 10 to 20? ). Let's assume the diagram: when we plot (-20^\circ\text{C}) (wait, the x - axis labels: - 10, - 8, - 6, - 4, - 2, 0, 2? Maybe the x - axis is mislabeled, or maybe it's a typo, and the temperature is, say, - 20 is to the left of - 10. Wait, maybe the diagram is for a different substance? No, the question is about ( \text{CO}_2 ). Wait, maybe I made a mistake. Wait, let's check the options. Option A: gas, B: liquid, C: solid, D: boiling point. At 1 atm, ( \text{CO}_2 ) does not have a liquid phase (because 1 atm is below the triple point pressure of ( \text{CO}_2 ), which is ~5.11 atm). So at 1 atm, ( \text{CO}_2 ) can be solid or gas. At (-20^\circ\text{C}) (which is warmer than the sublimation temperature at 1 atm, (-78.5^\circ\text{C})), so it should be gas. Wait, but maybe the diagram in the question is different. Wait, the diagram shows solid (left), liquid (middle), gas (right). Let's assume that at 1 atm (y - axis, 1 atm is low on the y - axis, since the y - axis goes up to 20 atm). So at 1 atm (low pressure) and (-20^\circ\text{C}) (x - axis, let's say - 20 is to the left of - 10), but maybe the diagram's x - axis is from, say, - 100 to 50. Wait, perhaps the question's diagram is a general phase diagram (not specific to ( \text{CO}_2 ) but a generic one), but the question says "phase diagram for ( \text{CO}_2 )". Wait, no, maybe the diagram is misdrawn, but according to the options, let's re - think. Wait, at 1 atm, ( \text{CO}_2 ) is gas at temperatures above (-78.5^\circ\text{C}). (-20^\circ\text{C}) is above (-78.5^\circ\text{C}), so it's gas. So option A.

Answer:

A. It is in the gas phase.