Any of the other alkali metals not mentioned (I.e. rubidium, caesium or francium). They are all group one metals meaning that they contain one valence (outer shell) electron so they will have similar properties. Francium is the most reactive alkali metal while lithium is the least reactive (if you’d like me to explain that let me know :) )
Answer:
-177.9 kJ.
Explanation:
Use Hess's law. Ca(s) + CO2(g) + 1/2O2(g) → CaCO3(s) ΔH = -812.8 kJ 2Ca(s) + O2(g) → 2CaO(s) ΔH = -1269.8 kJ We need to get rid of the Ca and O2 in the equations, so we need to change the equations so that they're on both sides so they "cancel" out, similar to a system of equations. I changed the second equation. Ca(s) + CO2(g) + 1/2O2(g) → CaCO3(s) ΔH = -812.8 kJ 2CaO(s) → 2Ca(s) + O2(g) ΔH = +1269.8 kJ The sign changes in the second equation above since the reaction changed direction. Next, we need to multiply the first equation by two in order to get the coefficients of the Ca and O2 to match those in the second equation. We also multiply the enthalpy of the first equation by 2. 2Ca(s) + 2CO2(g) + O2(g) → 2CaCO3(s) ΔH = -1625.6 kJ 2CaO(s) → 2Ca(s) + O2(g) ΔH = +1269.8 kJ Now we add the two equations. The O2 and 2Ca "cancel" since they're on opposite sides of the arrow. Think of it more mathematically. We add the two enthalpies and get 2CaO(s) + 2CO2(g) → 2CaCO3(s) and ΔH = -355.8 kJ. Finally divide by two to get the given equation: CaO(s) + CO2(g) → CaCO3(s) and ΔH = -177.9 kJ.
Either covalent compounds are neutral, covalent compounds share electrons
Answer:
The mass of an atom is found in its nucleus.
Explanation:
An atom is made of three different particles: protons, neutrons and electrons.
Protons (positive charge) and neutrons (no charge) each have a mass of 1 AMU. They are both found in the nucleus (centre) of the atom.
Electrons (negative charge) are considered to have a mass of 0. Their mass is not actually 0, but very close so we do not count them. They are not in the nucleus, but found in shells surrounding the atom.
To calculate the mass of an atom, we add the number of protons and the number of electrons.
m = P + N
