6.3 ×

In scientific notation, the numerical value without the exponent of 10 must be within the range from 1 to just below 10 (for example, 9.99...). In this case, 6.3 is already within this range, so we just have to multiply it by 1. To get a multiplier of 1 using base 10, we would have to raise 10 to the zeroth power.
2NH3(g) = N2(g) + 3H2(g)
Before decomposed :
P NH3 = 2.7 atm
After decomposed :
P N2 = 0.54 atm
P H2 = P N2 / 3 = 0.54 / 3 = 0.18 atm
P NH3 = 2.7 - 2(0.18) = 2.34 atm
Pressure equilibrium constant :
Kp = (P N2)(P H2)³ / (P NH3)²
Kp = (0.54)(0.18)³ / (2.34)²
Kp = 5.75 × 10^(-4)
3. I am not sure what is meant by shape, it could be to do with structure.
4. It is magnesium nitride, as adding nitrogen makes a nitride
It lecterns fries that is the answer.