Same time Life Appeared on Earth.
Let's eliminate these one by one.
The first pair would not be the same, as X would most likely be in group IA, and Y would be in group VIIA, because of their tendency to gain and lose electrons.
The second pair would also violate the same rule, but X would most likely be in group IIA, and Y would most likely be in group VIA.
The third pair would not be the same, as X is most likely in group VIIA, and since Y has eight valence electrons, it is most likely a noble gas.
The final pair has X with atomic number 15, making it phosphorous. Phosphorous wants to gain 3 electrons to have a full octet of 8 outer "valence" electrons, and Y would also like to gain 3 electrons. This means it is possible that the final pair would be in the same group.
Answer:
456 kJ
Step-by-step explanation:
CH₄ + 2Cl₂ ⟶ CCl₄ + 2H₂ ; ΔH = 45.6 kJ
Treat the heat as if it were a product in the equation. Then use the molar ratio (45.6 kJ/2 mol Cl₂) in the usual way.
Amount of energy = 20 mol Cl₂ × (45.6 kJ/2 mol Cl₂) = 456 kJ
You must add 456 kJ to react 20 mol of chlorine with excess methane.
I'm pretty sure that it is C. :)
HBr (aq) is an Arrhenius acid.
The equation is <span>HBr(aq) -> H+ + Br-</span><span> </span>