The standard enthalpy of formation of substance in its standard state is zero.
Enthalpy is defined as a thermodynamic quantity that describes the energy of a system. For substances in their standard state, the enthalpy of formation is zero.
The standard state of a substance is defined as the state in which it is found under standard conditions. The following substances has their standard ethalpy of formation as zero or not zero;
Zero enthalpy of formation Non zero enthalpy of formation
Cl2(g) I2(s)
Br(g) Br2(l)
I2(g) Br2(s)
Hg(l) Hg(s)
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Answer:
M (third main energy level)
Explanation:
The third main energy level bears the first appearance of the 'd' sublevel. The principal quantum number(n) depicts the main energy levels in which an orbital is located. It takes values of n=1,2,3,4,5..... and it can be represented by the shells k,l,m,n.......
The subshells in these main orbitals are represented by s,p,d and f. For the K shell, the principal quantum number is m and its sublevel notations are s,p and d. This is where the d-sublevel first appears.
D. precision. At first glance you can mark out A and B because the answers does not relate to the question. If question had said "what do you call it when the measurement is close to the actual answer" then you would have picked C. So that leaves you D. precision.
