Given the following reaction: 2 NO_(g) + O_2(g) rightarrow 2, NO_2(g) delta_rms

Question

Given the following reaction: 2 NO_(g) + O_2(g) rightarrow 2, NO_2(g) delta_rms H = - 114.2 kJ What is delta_rms H for this reaction? NO_2(g)rightarrow NO_(g) + 1/2O_2(g) Consider the following reaction: 2 H_2 + O _ 2 rightarrow 2 H_2O gelta_rmsH= -483.6 kj/mol a| Is this reaction endothermic or exothermic? Describe what is happening to the energy during this reaction. Calculate delta H if 3.50 g hydrogen gas are reacted in an abundance of oxygen. When 1.00 g of magnesium metal is burned to give magnesium oxide, 5.92 kj of heat are set free. heat are set free Determine delta_rms H for the reaction. 2 Mg + O_2rightarrow 2 MgO

Explanation / Answer

Q1) The given reaction is 2NO + O2 ----> 2NO2 and delta h for this = -114.2 kJ

When a thermodynamic equation is reversed, the DElta H has reverse sign .

thus for 2NO2---------> 2NO + O2 the delta H = +114.2 kJ

When the equation is divided by half, the value of delta H also divides by hlaf

Thus for

NO2---------> NO +1/2O2 the delta H = +114.2/2 kJ = + 57.1 kJ

Q2)

2H2 + O2 ---. > 2H2O delta H = -483.6kJ

a) this reactionis exothermic as the sign of Delta H is negative

It indicates energy in the form of heat is relased during the reaction.

b) when 2 moles of H2 = 2x2g/mol of H2 is reacted it give -483.6kJ of heat

If 3.5 g of H2 is reacted energy liberated = 3.5g x 483.6 kJ/2x2

=423.15 kJ of heat

3) 2Mg + O2 ----> 2 MgO

when 1 g of Mg is burnt as per reactionit gave 5.92 kJ of heat

If 2 moles of Mg that is 2x24 g of Mg burn in oxygen to give heat = ?

= 2 x 24 g x 5.92 kJ /1 g

= 284.16 kJ

The delta H of this reaction is = -284.16kJ

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