The potassium chloride is KCl. The gram formula mass of KCl is 39+35.5=74.5 g/mol which means 74.5 g per mole of KCl. So the mass of KCl is 6.90*74.5=514 g.
Answer:
From the following enthalpy of reaction data and data in Appendix C, calculate ΔH∘f for CaC2(s): CaC2(s)+2H2O(l)→Ca(OH)2(s)+C2H2(g)ΔH∘=−127.2kJ
ΔHf°(C2H2) = 227.4 kJ/mol
ΔHf°(H2O) = -285.8 kJ/mol and
ΔHf°(Ca(OH)2) = -985.2 kJ/mol
(Ans)
ΔHf° of CaC2 = -59.0 kJ/mol
Explanation:
CaC2(s) + 2 H2O(l) → Ca(OH)2(s) + C2H2 (g) = −127.2kJ
ΔHrxn = −127.2kJ
ΔHrxn = ΔHf°(C2H2) + ΔHf°(Ca(OH)2) - ΔHf°(CaC2)- 2ΔHf°(H2O);
ΔHf°(CaC2) = ΔHf°(C2H2) + ΔHf°(Ca(OH)2) - 2ΔHf°(H2O) – ΔHrxn
Where
ΔHf°(C2H2) = 227.4 kJ/mol
ΔHf°(H2O) = -285.8 kJ/mol and
ΔHf°(Ca(OH)2) = -985.2 kJ/mol
ΔHf°(CaC2) =227.4 - 985.2 + 2x285.8 + 127.2 = -59.0 kJ/mol
ΔHf°(CaC2) = -59.0 kJ/mol
Answer:
7 Valence Electrons.
Explanation:
The Valence electrons are referred to as the number of electrons in the outermost shell of an atom.
When given the electronic configuration, the valence can be calculated by adding the superscript of the hugest number coefficient.
The highest number coefficient in this electronc cnfiguration is 2. The sum of it's superscript is 2 (in 2s²) and 5 ( in 2p⁵). That is 2 + 5 = 7
How to test the answer?
The atom given has 9 electrons ( 2 + 2 + 5).
The K shell is being occupied by 2 electrons, the next shell; M shell which can occupy maximum of 8 electrons is being occupied by 7 electrons ( 9 - 7). And in this atom, the M shell is the outermost shell.