Which of the following statements explain why the van der waals equation must be used to describe real gases? x. interactions between gas molecules reduces the temperature of the gas in the sample y. the non-zero volumes of gas particles effectively decrease the amount of "empty space" between them z. the molecular attractions between particles of gas decreases the pressure exerted by the gas

Statements Y and Z.

Explanation:

The Van der Waals equation is the next one:

(1)

The ideal gas law is the following:

(2)

where n: is the moles of the gas, R: is the gas constant, T: is the temperature, P: is the measured pressure, V: is the volume of the container, and a and b: are measured constants for a specific gas.  

As we can see from equation (1), the Van der Waals equation introduces two terms that correct the P and the V of the ideal gas equation (2), by the incorporation of the intermolecular interaction between the gases and the gases volume. The term an²/V² corrects the P of the ideal gas equation since the measured pressure is decreased by the attraction forces between the gases. The term nb corrects the V of the ideal gas equation, taking into account the volume occuppied by the gas in the total volume, which implies a reduction of the total space available for the gas molecules.          

So, the correct statements are the Y and Z: the non-zero volumes of the gas particles effectively decrease the amount of "empty space" between them and the molecular attractions between gas particles decrease the pressure exerted by the gas.            

Have a nice day!

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%

the answer is c. nacl