Chem Question?! I don't understand how 2 do this!!?

Question

For each of the following processes: state whether it is exothermic or endothermic, identify whether the reactant or products have the higher enthalpy, and state whether heat would be released to or absorbed from the surroundings.

(a) burning kerosene
(b) melting ice
(c) condensing steam at 100 degrees Celsius

And could you please give reasons as well...thanks! :)

The reusable booster rockets of the space shuttle use a mixture of aluminium and ammonium perchlorate as fuel. An equation for the reaction is:

3Al (s) + 3NH4ClO4 (s) --> Al2O3 (s) + 3NO (g) + 6H2O (g) + 2677 kJ

Calculate how much heat is released when the following quantities of aluminium are consumed according to the above equation:

(a) 1 mol
(b) 1 kg

Please help me work out the 2 questions because I don't know how to do them...THANKS! :)

Answer 1

Definitions:
"exothermic" = the reaction yields heat to the surroundings in order to happen; "endothermic" = the reaction needs heat from the surroundings to happen;
"enthalpy" means "heat content inside" a substance: therefore, if a reaction is exothermic, ie. if it yields heat to the surroundings, that involves the products having less "heat inside" than the reactants. In other words, any reactions are balanced for both "matter" and "heat inside".

Your examples:
a) burning kerosene: kerosene is a hydrocarbon (ie. a compound of C and H), and when it burns (ie. when it reacts with O2, oxygen, in the air) it gives CO2 and H2O as products, and a lot of heat, of course! Consequently, the reaction (aka "combustion") is exothermic; the sum of enthalpies of products is lower than that of reactants.
b) no actual chemical reaction here, but a physical change of state "only"; you give heat to melt ice; therefore, the process is endothermic, and the product (ie, liquid water) have a higher enthalpy because it has taken in the heat you gave to the ice.
c) another physical change of state - steam to liquid water, where you have to cool down steam (ie, take away heat); all considerations are opposite to the b) case: therefore, exothermic process, enthalpy of the product is lower (ie, the "heat inside" of liquid water is lower than in steam.

2nd QUESTION.
First of all, you forgot AlCl3 among the products in the booster reaction!
The total heat released (2677 kJ) refers to 3 moles of Al: therefore, divide that amount by 3 and you will get the amount of heat for just one mole of Al. Molar Mass of Al is 27 g/mol, you have 3 moles there, ie, 81 g totally; therefore divide the total amount of heat (2677 kJ) by 81 and multiply it by 1000 - you will get the enthalpy for 1 kg of Al.

Answer 2

the three questions are equivalent, if you can answer one for a particular example, you can answer them all.

exothermic processes release heat to the surroundings since the reactants have higher enthalpy than the products. everything is reversed for endothermic processes: the products have higher enthalpy and heat is absorbed from the surroundings. these are simply definitions that you need to remember.

for the specific examples it's just a matter of general knowledge or observation: burning kerosene releases heat, melting ice absorbs heat, and condensing steam releases heat.

Answer 3

3Al (s) + 3NH4ClO4 (s) --> Al2O3 (s) + 3NO (g) + 6H2O (g) + 2677 kJ

3 moles of Al will produce 2677 kJ of energy. Since 1 mole is one-third of 3 moles, one-third of 2677 kJ will be produced by 1 mole of Al

Convery 1 kg (1000 g) of Al to moles. Let's just say it is 50 moles. To determine how much energy, use this ratio and proportion:

50 is to 3 as x is to 2677

For part a, the answer would be 1 is to 3 as x is to 2677.

Answer 4

Exothermic means that it releases energy (heat) into the surroundings.

Endothermic means that it absorbes energy (Heat) from the surroundings.

a. would be exothermic because you are releasing heat into the surroundings.
b. would be endothermic, because it is absorbing heat, therefore melting.
c. would be exothermic, because you are releasing energy.

I am 100% percent sure of this. Good luck!

Answer 5

The numbers are what share you have so case in point C= carbon and you could desire to paintings out what share atoms it has attempt using a periodic table because of the fact the two is what share you have of them so which you cases the atoms by using 2 and get the respond i will objective paintings that equation out for you presently.