lucarelli alkane/alkene/enthalpy

In exothermic reaction, delta H is negative and temperature of reaction mixture increases. What is significance of negative delta H value and why should this lead to increase in temperature for reaction mixture?

The energy stored within chemical bonds contributes to the enthalpy of a sunstance

during a chemical change chemical bonds within the reactions are broken and new chemical bonds within the products are formed

in exothermic reaction, this results in overall decrease in energy stored within chemical bonds (energy needed to break bonds is less than energy released when forming new bonds)

this results in heat energy being released into the reaction mixture and into surroundings (ie heat is now lost)

the loss of heat from the reaction mixture equates to reduction of its enthalpy and is signified by the negative value of delta H

TOTAL ENERGY IS CONSERVED AS THE LOST ENTHALPY REAPPEARS AS AN EQUIVALENT AMOUNT OF HEAT ENERGY IN THE SURROUNDINGS

by adding Br2(aq), can we distinguish between ethane and ethene gas? How?

By bubbling both gases into bromine water, the ethene will undergo addition reaction (and rapidly decolorize bromine water from orange to colourless) whereas ethane undergoes substitution reaction (and slowly decolorizes bromine water from orange to colourless)

by adding bromine water can we distinguish between hexene and benzene?

yes, hexene is an alkene so undergo addition reaction (rapidly decolourise bromine water from orange to colourless) whereas benzene undergo substitution reaction (slowly decolourise bromine water from orange to colourless)

what is the expected products and observations for ethane gas bubbled through bromine water and exposed to sunlight (UV rad)

expected products: bromoethane and HBr observation: Bromine water slowly fades from orange to colourless Signup and view all the answers

can a test with bromine water distinguish between the two isomers of C3H6?

yes, the two isomers are cyclopropane and propene. propene = alkene so undergo addition (rapidly decolourise bromine water from orange to colourless) whereas cyclopropane = aklane (saturated) so undergo substitution (bromine water slowly fades from orange to colourless) Signup and view all the answers

What are the products of the substitution reaction ethane plus chlorine water

chloroethane(g) + HCl(g) CH5Cl + HCl Signup and view all the answers

when barium hydroxide and ammonium chloride is mixed, a chemical reaction takes place causing the mixture to cool down,. since energy cannot be neither created nor destroyed, how can we account for the lost energy?

the reaction is endothermic meaning energy needed to break bonds of reactants is greater than energy released when forming bonds of products meaning there is INCREASE in energy stored within the chemical bonds of products as energy must be conserved, this results in a decrease in the kinetic energy of the particles in the surroundings the decreased particle average kinetic energy is expressed as a reduced temperature Signup and view all the answers