What is the molecular mass of a gas whose density is 1.25 grams per liter at STP?

STP = standard temperature and pressure

Use the formula:

d = MP/RT

where:

d = density = 1.25 g/L

M = molar mass (unknown)

P = pressure = 1 atm (standard pressure)

R = universal gas constant = 0.8206 L*atm/mol*K

T = temperature = 0C or 293.15 K (standard temperature)

1.25 g/L = M*(1 atm)/(0.08206 L*atm/mol*K)*(273.15 K)

M = 28.0 grams/mol

The correct answer is that fault Q took place prior to the deposition of layer K.

Explanation:

It can be observed in the diagram that fault Q is not crossing layer K, and it stops right underneath it, thus, this signifies that the formation of fault took place initially, then after a certain time period, the deposition of layer K took place.  

From the diagram, it is clear that the oldest layer is layer B, as it is present in the bottom. The youngest is layer K as it is the topmost layer.