1. I is true; II is true: what do you think of III?
2. Higher charge and smaller radius gives higher lattice energy.
Which statements are correct for an endothermic reaction?
I. The system absorbs heat.
II. The enthalpy change is positive.
III. The bond enthalpy total for the reactants is greater than for the products.
A. I and II only B. I and III only
C. II and III only D. I, II and III
The answer is A but I don't understand Why D is not correct
2) Which combination of ionic charge and ionic radius give the largest lattice enthalpy for an ionic
compound?
Ionic charge Ionic radius
A. high large
B. high small
C. low small
D. low large
The answer is D but Why B is not correct
Please help me,,thank you so much
3 answers
I based on the formular to calculate enthalpy change is equal to the bond enthalpy total for the reactants subtracting from the bond enthalpy for products.Hence,if the reaction is endothermic,then the bond enthalpy total for the reactants is greater than for the products
Bond-dissociation energy ΔH(dissociation) is the energy required to break one mole of a particular type of covalent bond in a gas-phase compound.
Energies of some bonds can differ from compound to compound, so we use an average bond energy.
Energies of some bonds can differ from compound to compound, so we use an average bond energy.