Given the standard heat of combustion of methanol ch3oh is 182.6

kcal/mol, dimethyl ether ch3och3 is 347.6 kcal/mol, (methanol/

dimethyl ether in gas phase, water in liquid phase). given the heat

of vaporization of water is 10 kcal/mol, methanol is 8.4 kcal/mol,

dimethyl ether 4.8 kcal/mol. calculate the reaction of dehydration

of methanol to produce dimethyl ether. (indicate the phase of your

components).

Explanation:

The given reaction equation showing heat of combustion  is as follows.

    ....... (1)

So, for 2 mol methanol the value for heat of combustion is as follows.

              2 mol x 182.6 Kcal/mol = -365.2 Kcal

Now, -347.6 kcal/mol

When we reverse the 2nd reaction

      heat of reaction +347.6 kcal {sign reversed with reaction}  ........ (2)

Now, adding equatio (1) and (2) we get the following.

Now, heat of combustion will also be added.

             +347.6 kcal +(-365.2 Kcal)

            = -17.6 Kcal

Since, the reaction occurs at STP , water will be in liquid state as B.P =

So, energy needed for water to convert to vapour = 1 mol x 10 Kcal/mol = 10 Kcal, and it will be absorbed by water to form vapor .

Hence, heat of dehydration =

                                              = - 8.8 Kcal/mol

Therefore, the net calorific value for this after water is evaporated to form gas = 17.6 - 10 = 7.6 Kcal

or,            

                    = 3.8 Kcal/mol

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j

- decrease the number of plants and animals living in the water.