Name. Constants and Equations: Speed of light Planck constant Conversion factor

Question

Name. Constants and Equations: Speed of light Planck constant Conversion factor -2.998 x 10 m/'s h-6626x 104Js 1nm 104 m Heat gained or lost based on specific heat, mass, and -CmxAT temperature change Standard enthalpy change of a reaction H'-EaH(products)-2mite reactant) (bond enthalpies of bonds forned) E- bv The reaction enthalpy as a function of average bond AH (hond centhalpies of bonds b of bonds broken) enthalpies for reactions Light as a wave Light as a particle, the energy of photon Energies of the allowed slates of the hydrogen atomE-(21S 10) You MUST show all work or you will get no credit for your answer. In all questions involving calculations, incorrect significant figures will cost 0.5 point 1. (12 points) Consider the following reaction: (a) (2 points) Is this reaction exothermic or endothermic? (b) (5 points) Calculate the amount of heat transferred when 24.0 g of CHiOH(g) is decomposed by this reaction at constant pressure. (CHOH: 32.0 g/mol) (c) (5 points) For a given sample of CHOH, the enthalpy change during the reaction is 82.1 kJ. How many grams of methane gas CH are produced? (CHe: 16.0 g/mol)

Explanation / Answer

a)

this reaction has positive dH, therefore, requires energy to react, this must be endothermic

b)

m = 24 g of CH3OH decomposed

mol = mass/MW = 24/32 = 0.75 mol

then..

Q = n*HRxn = 0.75*252.8 = 189.6 kJ will be released

c)

find moles of methane produced

n = Q/Hrn = 82.1/252.8 = 0.3247 mol of CH3OH reacts

ratio is:

1 mol of CH3OH = 1 mol of CH4

0.3247 mol of CH4 produced

mass = mol*MW = 0.3247*16 = 5.1952 g of CH4

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