chem

a considerable amount of heat is required for the decomposition of aluminum oxide.
2Al2O3-> 4Al(s)+ 3O2(g)
change in heat= 3352KJ
a. what is the heat change for the formation of 1 mol of aluminum oxide from its elements?
i got this one. my answer is -1676.0KJ
but i didn't get part b.
b. is this reaction exothermic or endothermic?
i assumed that this would be exothermic because the change in heat is -1676.oKJ.
but the answer is endothermic. Help?

  1. 👍
  2. 👎
  3. 👁
  1. The heat given in the problem is for the reaction as written so it is endothermic because the sign is +. That's part b.
    Part a, the problem asks for the heat of FORMATION which is the other direction so the heat is -3352 kJ/2 mol which makes it -1676 kJ/mol.
    I think you assumed the b part was asking for the same reaction as part a which is the formation. I don't read it that way.

    1. 👍
    2. 👎
  2. oh okay thanks!

    also what would be considered as a free element?
    would 4Al be one?

    1. 👍
    2. 👎
  3. yes
    Al is a free element. Oxygen is a free element. ANY element in the periodic table is a "free" element. When it is combined with another element (or elements), it isn't free any more.

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. Chemistry

    The amount of heat required to raise 200 g of aluminum by 10 degrees celsius if its specific heat is 0.897 J/gC ? I need help. This is all confusing.

  2. Chemistry

    Consider the following reaction: 2Fe2O3 --> 4Fe + 3O2 ∆Hrxn° = +824.2 kJ The decomposition of 29.0 g of Fe2O3 results in a. the release of 150 kJ of heat b. the release of 12000 kJ of heat c. the absorption of 12000 kJ of heat

  3. Chemistry

    The specific heat of aluminum is 0.900*j/g*C How much heat is required to raise the temperature of a 30.0 g block of aluminum from to 25.0 oC to 75 oC?

  4. Chemistry (Regents level)

    1- In the reaction Fe2O3 + 3 CO = 2 Fe + 3 CO2, what is the total number of moles of CO used to produce 112 grams of iron? a) 1.0 b)2.0 c)3.0 d)4.0 2- Given the reaction: 4Al + 3O2 = 2Al2O3 How many moles of Al2O3 will be formed

  1. Chemistry

    Solid aluminum and gaseous oxygen react in a combination reaction to produce aluminum oxide: 4Al (s) + 3O2 (g) →→ 2Al2O3 (s) The maximum amount of Al2O3 that can be produced from 2.5 g of Al and 2.5 g of O2 is ________ g.

  2. Chemistry

    Classify the following reactions as precipitation reactions, oxidation-reduction reactions, or acid-base reactions. 1)2NaCl(aq)+K2H2Sb2O7(aq)==Na2H2SbO7(s)+2KCl(aq) 2)(CH3COO)2Cu(aq)+(NH4)2C2O4(aq)==CuC2O4(s)+2CH3COONH4(aq)

  3. chemistry

    can you calculate the mass(g) of AL2O3 that is produced when 2.5g of aluminum and 2.5g of oxygen react according to this equation : 4Al(s)+3O2(g)->2Al2O3(s) im not understanding how to do this

  4. Chemistry

    how many grams of Al2O3 be obtained if 13.5 g of aluminum completely reacts with oxygen as 4Al+3O2---->2Al2O3 Molar mass of Al is 27g/mol.

  1. Chemistry

    1. Aluminum reacts with oxygen to produce aluminum oxide which can be used as an adsorbent, desiccant or catalyst for organic reactions. 4Al(s) + 3O2(g) → 2Al2O3(s) A mixture of 82.49 g of aluminum ( Picture = 26.98 g/mol) and

  2. Chemistry

    Calculate the amount of heat released in the complete combustion of 8.17 grams of Al to from Al2O3 at 25 celcius and 1 atm. The delta enthalphy change in the heat of formation for Al2O3 = 1676 KJ/mol 4Al(s) + 3O2(g) --> 2Al2O3(s)

  3. Chemistry

    Given 2Al2O3 (s) --> 4Al(s) + 3O2 (g) (standard enthalpy change= 3351.4 kJ) a) What is the heat of formation of aluminum oxide? How do I find heat of formation from standard enthalpy change? I know how to do it when I'm given

  4. Chemistry

    Bauxite ore contains aluminum oxide Al2O3(s) which is decomposed using electricity to produce aluminum metal and oxygen gas. What mass of aluminum metal can be procuced from 155g of aluminum oxide?

You can view more similar questions or ask a new question.