After one half-life (4.5 billion years), what percent of the original uranium remains? After two half-lives (9 billion years), what percent of the original uranium remains?

After three half-lives (13.5 billion years), what percent of the original uranium remains?

After four half-lives (18 billion years), what percent of the original uranium would remain?

)benzene and toluene form nearly ideal solutions. consider an equimolar solution of benzene and toluene. at 20 °c the vapour pressures of pure benzene and toluene are 9.9 kpa and 2.9 kpa, respectively. the solution is boiled by reducing the external pressure below the vapour pressure. calculate (i) the pressure when boiling begins, (ii) the composition of each component in the vapour, and (iii) the vapour pressure when only a few drops of liquid remain. assume that the rate of vaporization is low enough for the temperature to remain constant at 20 °c.