C. The difference<span>ce</span><span /><span> between the potential energy of the products and the potential energy of the reactants
</span>
Answer:
A) Charging by contact
Explanation:
Transfer of heat by direct contact, Heat energy is conducted from the hotter medium to the cooler medium
They have used added new elements to the table .
<u>Explanation:</u>
As new elements are discovered chemists add them to the period table leading to the periodic table undergoing continuous modifications. When the first periodic table in the world was formed, very few elements were known to humankind. Earlier periodic tables thus contain lesser number of elements than the modern ones.
Mendeleev's periodic table contained 63 elements arranged in the increasing order of their atomic masses. Modern periodic tables have far more number then the older ones like that of Mendeleev's and the elements are arranged in the order of their atomic numbers.
Answer:
- 416 kJ/mol
Explanation:
The standard enthalpy of the reaction (Δ
H
∘
rxn) is independent of the pathway, so it can be calculated by the enthalpy of formation of the reactants and the products:
Δ
H
∘
rxn = ∑n*Δ
H
∘f products - ∑n*Δ
H
∘f reactants
Where n is the number of moles in the balanced reaction. So, for the reaction given:
Na₂O(s) + 1/2O₂(g) → Na₂O₂(s)
Because O₂ is formed by only one elements, its Δ
H
∘f is 0 kJ/mol:
-89.0 = (1*(-505) - (1*Δ
H
∘fNa₂O)
Δ
H
∘fNa₂O = -505 + 89
Δ
H
∘fNa₂O = - 416 kJ/mol
Crystal structure is fluorite
