A. N₂ (g) + 3 H₂ (g) --> 2 NH₃ (g)
B. The value for standard enthalpy of formation is empirical given that the reactants involved were pure elements. So, you can search this on the internet or in any textbook. The Hf for NH₃ is -46.0 kJ/mol.
C. C (s) + O₂ (g) --> CO₂ (g)
D. The Hf for CO₂ is <span>-393.5 kJ/mol
E. 4 Fe (s) + 3 O</span>₂ (g) --> 2 Fe₂O₃ (s)
F. The Hf for solid Fe₂O₃ is -826.0 kJ/mol.
G. C (s) + 2 H₂ (g) --> CH₄ (g)
H. The Hf for methane gas is -74.9 kJ/mol.
Time to decay : 2040 years
Further explanation
The atomic nucleus can experience decay into 2 particles or more due to the instability of its atomic nucleus.
Usually radioactive elements have an unstable atomic nucleus.
The main particles are emitted by radioactive elements ,so that they generally decay, are alpha (α), beta (β) and gamma (γ) particles
General formulas used in decay:
T = duration of decay
t 1/2 = half-life
N₀ = the number of initial radioactive atoms
Nt = the number of radioactive atoms left after decaying during T time
moles zirconium :

moles niobium :

the half-life of niobium-91 is 680 years
Reaction
⁹¹₄₁Nb ⇒⁹¹₄₀Zr + ₁⁰e
Amount of Nb from reaction : 0.169
Amount of initial Nb = 0.0242 + 0.169 = 0.1932
Time to decay (T) :

At STP, one mole of gas occupies 22.4 L of space. Assuming the conditions conform to STP
volume CO2 = 0.5 mol * 22.4 L/1 mol
= 11.2 L
= 10 L
The answer with 1 significant figure is 10 L of CO2
Answer: orderly arrangement of particles
Explanation:
In a crystaline solid, the particles that compose the solid are arranged or packed in an orderly manner to form a three dimensional crystal lattice with a defined structure. Sodium chloride is a crystaline solid.
In an amorphous solid, the particles that compose the solid aren't arranged in an orderly manner hence the solid tends to be brittle, e.g glass