Measurements show that the enthalpy of a mixture of gaseous reactants increases by 130. kJ during a certain chemical reaction, which is carried out at a constant pressure. Furthermore, by carefully monitoring the volume change it is determined that -137. kJ of work is done on the mixture during the reaction.

167 kJ

Explanation:

Given parameters

Change in enthalpy = 130 kJ (decrease)

Work done = -137 kJ

Change in energy, \delta = ?  

From the first law of thermodynamics:

ΔH = ΔE + PΔV,

Where, ΔH= change in enthalpy

ΔE = change in Internal energy  

Substituting values into the above formula —  

130 kJ = ΔE + -137  kJ

130 kJ = ΔE - 137 kJ

therefore,

ΔE = (130 + 137 ) kJ

ΔE = 167 kJ

Therefore, the change in energy of the gas mixture during the reaction is 167 kJ.  

Since the value of energy change Is positive, therefore this Is endothermic reaction  

pure substance: iron,copper

impure substance: water,charcoal

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)