Answer:
oxygen is an element because it is a pure substance which cannot be split into simpler substances by chemical means
A positive cahnge of enthalpy, ΔH rxn = + 55 kJ/mol, for the forward reaction means that the reaction is endothermic, i.e. the reactants absorb energy and the products are higher in energy.
Activation energy is the difference in the energy level of the reactants and the peak in the potential energy diagram (the energy of the transition state).
For an endothermic reaction, the products will be closer in energy to the transition state than what the reactans will be; so, the activation energy of the reversed reaction is lower than the activation energy of the forward reaction.
Activation energy of reverse and forward reactions is related by:
Activation energy of reverse rxn = Activation energy of forward rxn - ΔH rxn
=> Activiation energy of reverse rxn = 102 kJ/mol - 55 kJ/mol = 47 kJ/mol
Answer: 47 kJ/mol
Answer:

Explanation:
The half-cell reduction potentials are
Ag⁺(aq) + e⁻ ⇌ Ag(s) E° = 0.7996 V
Fe²⁺(aq) + 2e⁻ ⇌ Fe(s) E° = -0.447 V
To create a spontaneous voltaic cell, we reverse the half-reaction with the more negative half-cell potential.
The anode is the electrode at which oxidation occurs.
The equation for the oxidation half-reaction is

26g --- 1 mol
56g --- X
X= 56/26 = 2,154 mol
959 ml = 959cm³ = 0,959dm³
C = n/V
C = 2,154/0,959
C = 2,246 mol/dm³