Chemistry, 25.12.2019 15:31 sofiisabella10

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a calorimeter is a device used to measure how much heat energy is taken in or given off in a reaction. suppose after five trials of a chemical reaction, 200 kj of heat was taken in on average. what conclusion can be made about the reaction? a. it is endothermic
.b. it releases heat energy.
c. it is a combustion reaction.
d. it creates more than one product.

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Answer from: libi052207

Option (A) is the correct answer.

Explanation:

A chemical reaction where heat energy is absorbed by the reactant molecules is known as an endothermic reaction.

For example, $A + B + Heat \rightarrow AB$

The value of $\Delta H$ = +ve for an endothermic reaction.

On the other hand, a chemical reaction in which heat energy is released by the reactant molecules is known as an exothermic reaction.

For example, $C + D \rightarrow CD + Heat$ is an exothermic reaction.

As 200 kJ of heat was taken in on average by the calorimeter so, it means heat energy is absorbed by the calorimeter.

Thus, we can conclude that the given reaction is endothermic in nature.

Answer from: Quest

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in $h_{2}s$ , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between $h_{2}s$ molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent $h_{2}s$ molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.

Answer from: Quest

answer: the value of enthalpy change will be -152.80 kj.

solution:

pressure = 1atm , temperature = $25^oc$ = 298 k $)0^oc=273kelvins$

$o_3+3no\rightarrow 3no_2,\delta h_{reaction}=? [/)</p><p>[tex]\delta h_{no}=90.4kj/mol$

$\delta h_{no_2}=33.85kj/mol$

$\delta h_{o_3}=142.2kj/mol$

$\delta h_{reaction}=\sum \delta h_{products}-\sum\delta h_{reactants}=3\times\delta h_{no_2}-(3\times \delta h_{no}+\delta h_{o_3})$

$\delta h_{reaction}=33.85-(90.4+142.2)=-311.85kj/mol$

given that pressure and temperature are same in both gases , the number of moles of both gases can be determined by the ideal gas equation.

$v_{no}=12.00 l,v_{o_3}=8.50 l$

$pv_{no}=n_{no}rt=1atm \times 12.00 l=n_{no}\times 0.0821 atml/k mol \times 298 k$

$n_{no}=0.49 moles$

$pv_{o_3}=n_{o_3}rt=1atm \times 8.50 l=n_{o_3}\times 0.0821 atml/k mol \times 298 k$

$n_{o_3}=0.34 moles$

according to reaction 3 moles no are reacting with 1 mol of $o_3$ ,then 0.49 mol of no will react with $\frac{1}{3}\times 0.49$ moles of ozone that is 0.16 moles of ozone. since, no is limiting reagent and $o_3$ is an excessive reagent.

enthalpy change for the reaction between the given volumes of the gases is :

$\delta h_{reaction}\times \text{moles of no}=-311.85kj/mol\times 0.49 mol=-152.80kj/mol$

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