Passage V

When rocks are melted at very high temperatures beneath Earth's surface, magma (molten rock) is formed. The gases CO2, and H2O can dissolve in magma. Figure 1 shows, for 4 different magmas (leucitite, basanite, rhyolite, and tholeiitic basalt), how the solubility of CO2 in the magma at 1,150°C varies with pressure (in megapascals MPa).

Figure 2 shows, at 3 different pressures, how the solubility of CO2 in rhyolite magma varies with temperature.

Figure 3 shows, at 4 different pressures, how the solubility of CO2, in rhyolite magma at 750°C varies with the weight percent of H2O in the magma.

33. Consider the solubility of CO2 in rhyolite magma at 750°C and 200 MPa, as shown in Figure 2. According to Figure 3, this rhyolite magma has a weight percent of H2O closest to which of the following?

Answer and Explanation

Your Answer is

Correct Answer is A

Explanation

Look at Figure 2 first, corresponding to the line of 200 MPa, when the abscissa is 750°C, the ordinate solubility is about 1500;

Look at Figure 3 again, still corresponding to the 200 MPa line, the ordinate solubility When it is 1500, the abscissa is 0.