Live practice

Apply Hess law to C(graphite)+2H₂→CH₄, followed by methane combustion.

The rule predicts that many main-group atoms gain, lose or share electrons to attain eight valence electrons. It helps rationalise common ionic and covalent formulae but fails for incomplete octets, odd-electron species and expanded valence shells.

Its outer configuration after radon is 5f¹⁴6d¹⁰7s²7p². The highest n is 7, and ns²np² is the group-14 pattern.

Convert the wavelength to metres, then use ν=c/λ and wavenumber =1/λ.

Convert the volume to litres, calculate the amount from n = MV, and then use m = nMₘ.

Principle and reasoning. Work from the governing physical relation and apply it to every stated part.

For the fixed gas amount, PV/T is constant. Pressure at depth includes the hydrostatic term.

Principle and reasoning. Work from the governing physical relation and apply it to every stated part.

Internal-energy change depends only on endpoints. Use the first law ΔU=Q−W, with W positive when done by the gas.

Principle and reasoning. Work from the governing physical relation and apply it to every stated part.

Pressure equals normal force divided by contact area.

Choose the initial direction as positive. The retarding force produces a negative acceleration.

Principle. Use definitions, the triangle inequality, and the fact that a zero sum makes any one vector a linear combination of the other two.