1. True or False: A. C 2 H 4 is a saturated compound. B. There are a number of s

Question

1. True or False:

    A. C2H4 is a saturated compound.

    B. There are a number of structures with the formula C6H14

     C. In hydrocarbons C atoms have 4 covalent bonds.

    D. water molecules are polar

    E. A mole of CH4 and a mole of CO2 have different numbers of molecules.

  F. Alkane molecules can react together to form polymers

    G. Generally ionic compounds have higher melting temperatures than covalent compounds.

    H. All chemical reactions are exothermic.

    I. When liquid water freezes heat is absorbed.

    J. All metals have the same specific heat

2. A. How many grams are in 2.75moles of C12H22O11

    B. How many moles are in 327 grams of K2SO4 ?

3. Considering the reaction:

                 2Fe2O3 + 3C   4Fe + 3CO2

     A. How many moles of C are needed to react with 6.00 moles of Fe2O3 ?

     B. How many grams of Fe result when 175g of Fe2O3 react ?

4. Using the bond energies below determine the value and sign of delta H for

              H-S-H + Cl-Cl Cl-S-Cl + H-H

    Bond energies in kJ/mol:

        H-S 365        Cl-Cl 240     Cl-S 255      H-H 432

5. Will a 1.0m solution of ZnCl2 in water have the same freezing temperature as

     A 1.0m solution of NaCl in water? Give a reason for your answer.

6. Explain why each of the following does not exist:

     A. CH2   B. C8H20   C. C3H2   D. CCl5   E. KCl3

7. Al metal has a specific heat of 0.880 J/gram-degree C. How many joules of heat

     are needed to heat 562grams of Al from 25.0oC to 95.0oC ?

8. The enthalpy of combustion of C2H6 is 1541kJ/mole. How many kJ of heat result

     when 775 grams of C2H6 are combusted ?

9. Explain why although both NaCl and sucrose, C12H22O11 , are soluble in water

     one of their solutions conducts electricity, but the other does not.

10. A sample of a hydrate of NiCl2 weighing 0.235 grams is heated to drive off the

      water leaving a weight of 0.128 grams. What is the formula of the hydrate ? i.e.

      What is the value of X in NiCl2(XH2O)

Explanation / Answer

1).A. C2H4 is a saturated compound. ===> False

B. There are a number of structures with the formula C6H14 ===> True

C. In hydrocarbons C atoms have 4 covalent bonds.===> True

D. water molecules are polar ===> True

E. A mole of CH4 and a mole of CO2 have different numbers of molecules ===> False

F. Alkane molecules can react together to form polymers ===> False

G. Generally ionic compounds have higher melting temperatures than covalent compounds. ===> True

H. All chemical reactions are exothermic.===> False

I. When liquid water freezes heat is absorbed. ===> False

J. All metals have the same specific heat ===> Fasle

2) A. How many grams are in 2.75moles of C12H22O11 ===> mass = moles X molar mass = 2.75 X 342 ==> 940.5 grams.

B. How many moles are in 327 grams of K2SO4 ===> moles = mass/ molar mass ==> 327/174 = 1.88 moles.

3) Considering the reaction:

                 2Fe2O3 + 3C   4Fe + 3CO2

   A. How many moles of C are needed to react with 6.00 moles of Fe2O3 ===> 2 moles of Fe2O3 nedds 3 moles of C then 6 Fe2O3 moles of needs 9 moles of C.

6. Explain why each of the following does not exist:

     A. CH2   B. C8H20   C. C3H2   D. CCl5   E. KCl3

A.CH2 = Carbon is a teravalent atom, but here it is bonded to two hydrogens only.

B. C8H20 = It is not an alkane(CnH2n+2),alkene(cnH2n) or alkyne(cnH2n-2)

C.C3H2 = Carbon is a teravalent atom, but here it is bonded to two hydrogens only.

D. CCl5 = Carbon is a teravalent atom, but here it is bonded to Five Chlorine atoms.

E. KCl3 = K is a monovalent atom.

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