Sickle-cell anemia is caused by: Group of answer choices a substitution of a serine residue for a glutamic acid residue at the beta-6 position a substitution of glutamic acid residue for histidine at the C terminus of the alpha chain a substitution of a glutamic acid residue for a phenylalanine residue at the beta-6 position a decreased production of alpha chains of hemoglobin polymerization of hemoglobin

)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.