Use the following data to calculate the standard heat (enthalpy) of formation, δ h°f, of manganese(iv) oxide, mno2 ( s). 2mno2( s) → 2mno( s) + o2( g), δh = 264 kj mno2( s) + mn( s) → 2mno( s), δh = -240 kj(a) -504 kj (b) -372 kj (c) -24 kj (d) 24 kj

(A)

Explanation:

The enthalpy of formation of a substance is the enthalpy of the reaction where this substance is formed by its constituents species. So, for MnO2, the enthalpy of formation is the enthalpy of the reaction:

Mn(s) + O2(g) --> MnO2(s)

By the Hess' law, when a reaction follows steps, the enthalpy of the overall reaction is the sum of the enthalpy of the steps. In this sum, the intermediaries must be canceled, so, some changes may have to be done in the reactions. If the reaction is inverted, the signal of the enthalpy inverts too, and if it's multiplied by some constant, the enthalpy is multiplied too.

2MnO2 (s) --> 2MnO(s) + O2(g) ΔH = 264 kJ (must be inverted)

MnO2(s) + Mn(s) --> 2 MnO(s) ΔH = -240 kJ

O2(g) + 2MnO(s) --> 2MnO2(s) ΔH = -264 kJ

MnO2(s) + Mn(s) --> 2 MnO(s) ΔH = -240 kJ

MnO is canceled, and 2MnO2 - MnO2 = MnO2 in the products because it was where have more of it:

O2(g) + Mn(s) --> MnO2(s)

ΔH = -264 + (-240) = -504 kJ

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.

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the atomic number of carbon is six, which means that a carbon atom has six protons. carbon has three naturally occurring isotopes: carbon-12, carbon-13, and carbon-14. which of these statements are true about carbon and its isotopes? select all that appl