A solution of benzene and toluene at 25 °C exerts a total vapor pressure of 66.6 torr. What is the mole fraction of benzene in the vapor phase? The vapor pressures of pure benzene and toluene at 25 °C are 94.2 torr and 28.4 torr, respectively. 0

0.5805.

Explanation:

Using Raoult's Law;

Psol = Xbenzene * P°benzene + Xtoluene * P°toluene

where,

Psol = vapor pressure of the solution

Xbenzene = mole fraction of benzene

P°benzene = vapor pressure of pure benzene

Xtoluene = mole fraction of toluene

P°toluene = vapor pressure of pure toluene

Mole fraction is defined as the ratio between the number of moles of a component in a solution to the total number of moles in the solution.

Xbenzene + Xtoluene = 1

Let,

Y = mole fraction of toluene

X = mole fraction of benzene

X = 1 − Y

Psol = X * P°benzene + (1 − X) * P°toluene

66.6 = X * 94.2 + (1 − X) * 28.4

X = 0.5805

Therefore,

Y = 1 - 0.5805

= 0.4195

Mole fraction of benzene = 0.5805.

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation:

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.