In descending order from top:
E
F
D
A
C
B
All you really need to do is remember the symbols of each, and you’ve got it.
Answer:
- <u><em>It is positive when the bonds of the product store more energy than those of the reactants.</em></u>
Explanation:
The <em>standard enthalpy of formation</em>, <em>ΔHf</em>, is defined as the energy required to form 1 mole of a substance from its contituent elements under standard conditions of pressure and temperature.
Then, per defintion, when the elements are already at their standard states, there is not energy involved to form them from that very state; this is, the standard enthalpy of formation of the elements in their standard states is zero.
It is not zero for the compounds in its standard state, because energy should be released or absorbed to form the compounds from their consituent elements. Thus, the first choice is false.
When the bonds of the products store more energy than the those of the reactants, the difference is:
- ΔHf = ΔHf products - ΔHf reactants > 0, meaning that ΔHf is positive. Hence, the second statement is true.
Third is false because forming the compounds may require to use (absorb) or release (produce) energy, which means that ΔHf could be positive or negative.
Fourth statement is false, because the standard state of many elements is not liquid. For example, it is required to supply energy to iron to make it liquid. Thus, the enthalpy of formation of iron in liquid state is not zero.
It is true that substances that have a high melting point and conduct electricity in the liquid phase are ionic substances, and if one of your options is NaCl, then that is the correct answer.
Answer:
VP (solution) = 171.56 mmHg
Explanation:
Vapor pressure of pure solvent(P°) - Vapor pressure of solution (P') = P° . Xm
Let's replace the data:
173.11 mmHg - P' = 173.11 mmHg . Xm
Let's determine the Xm (mole fraction for solute)
Mole fraction for solute = Moles of solute / Total moles
Total moles = Moles of solute + moles of solvent.
Let's determine the moles
Moles of solvent → 623.4 g / 119.4 g/mol = 5.22 moles
Moles of solute → 9.322 g / 180.1 g/mol = 0.052 moles
Total moles = 0.052 + 5.22 = 5.272 moles
Xm = 0.052 moles / 5.272 moles = 0.009 → 9/1000
173.11 mmHg - P' = 173.11 mmHg . 9/1000
P' = - (173.11 mmHg . 9/1000 - 173.11 mmHg)
P' = 171.56 mmHg
Answer:
No. of electrons of the element
