Question

QUESTION 26

The oxidation number of hydrogen in both sides of the following reaction 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O, are the same. What is that number?

A		0
B		+1
C		-1
D		There is not enough information to tell.

QUESTION 34

How many kJ of heat are produced for each gram of oxygen consumed in a combustion?

	A	4.184 kJ
	B	31.0 kJ
	C	13.0 kJ
	D	0.905 kJ

QUESTION 35

What is the oxidation number of carbon in the products of this reaction 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O?

	A	+4
	B	0
	C	-4
	D	There is not enough information to tell.

QUESTION 53

According to the following gaseous reaction H2 (g) + Cl2 (g)  2 HCl(g), if a liter of hydrogen and a liter of chlorine react, what is the volume of the final mixture?

A		1/2 liter
B		1 liter
C		2 liters
D		Not enough information to tell

Answer 1

26) The general oxidation state of H in its compounds is +1 .

So the oxidation state of hydrogen in C2H6 is +1

                                                   in H2O is +1

Therefore option B is correct

27) The balanced reaction is 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O :

Molar mass (g/mole)                              32

ΔH =ΔH⁰_fproducts –ΔH⁰_freactants

ΔH = [(4x ΔH⁰_fCO2(g) )+ (6 x ΔH⁰_{fH2O (l)} )]- [( 2 x ΔH⁰_fC2H6(g) )+ (7 x ΔH⁰_{fO2 (g)} )]

    = [(4x(-393.51))+(6x(-285.83))] - [(2x(-84.7))+ (7x0)] kJ/mol

    = -3119.6 kJ

For 7 moles = 7 x 32 g of O2 the liberated heat is 3119.6 kJ

For 1 g of Oxygen the liberated heat is 3119.6/(7x32) = 13.9 kJ

Therefore option (c) is correct.

34) The general oxidation state of H is +1 and that of O is -2

The sum of the oxidation states of all the elements in the given compound is equal to its charge

In CO2

Let x be the oxidation state of C then

x + 2(-2) = 0

   x = +4

Therefore option A is correct

35) 1 mole of H2 reacts with 1 mole of Cl2 produces 2 molesw of HCl

1 L of H2 reacts with 1 L of Cl2 produces 2 L of HCl

So the volume of the reaction mixture is 2 L( all the reactants are consumed)

Therefore option C is correct