Chemistry, 02.03.2020 23:21 raprocksbob

Which of the following reactions is not spontaneous? Cu (s) + 2HCl (aq) → CuCl2 (aq) + H2 (g) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2(g) 2Ni (s) + H2SO4 (aq) → Ni2SO4 (aq) + H2 (g) 2Al (s) + 6HBr (aq) → 2AlBr3 (aq) + 3H2 (g) Zn (s) + 2HI (aq) → ZnI2(aq) + H2 (g)

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Answer from: myaj580

Answer : The reaction not spontaneous is:

$Cu(s)+2HCl(aq)\rightarrow CuCl_2(aq)+H_2(g)$

Explanation :

The given reactions are the examples of single displacement reactions.

Single displacement reactions : It is defined as the reactions in which most reactive metal displaces the least reactive metal from its chemical reaction. The reactivity of metals is given by the series known as reactivity series.

That means the metals that lie above in the series can replace the metals which lie low in the reactivity series.

For the given options:

Option A :

$Cu(s)+2HCl(aq)\rightarrow CuCl_2(aq)+H_2(g)$

Copper lies low in the series than hydrogen and hence is less reactive. So, it will not displace hydrogen. Thus, this is a non-spontaneous reaction.

Option B :

$Mg(s)+2HCl(aq)\rightarrow MgCl_2(aq)+H_2(g)$

Magnesium lies above in the series than hydrogen and hence is more reactive. So, it will easily displace hydrogen. Thus, this is a spontaneous reaction.

Option C :

$2Ni(s)+H_2SO_4(aq)\rightarrow Ni_2SO_4(aq)+H_2(g)$

Nickel lies above in the series than hydrogen and hence is more reactive. So, it will easily displace hydrogen. Thus, this is a spontaneous reaction.

Option D :

$2Al(s)+6HBr(aq)\rightarrow 2AlBr_3(aq)+3H_2(g)$

Aluminum lies above in the series than hydrogen and hence is more reactive. So, it will easily displace hydrogen. Thus, this is a spontaneous reaction.

Option E :

$Zn(s)+2HI(aq)\rightarrow ZnI_2(aq)+H_2(g)$

Zinc lies above in the series than hydrogen and hence is more reactive. So, it will easily displace hydrogen. Thus, this is a spontaneous reaction.

Hence, the reaction not spontaneous is:

$Cu(s)+2HCl(aq)\rightarrow CuCl_2(aq)+H_2(g)$

Which of the following reactions is not spontaneous? Cu (s) + 2HCl (aq) → CuCl2 (aq) + H2 (g) Mg (s)

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 :

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

Answer from: Quest

frequency, z, and the collision density, z, in carbon dioxide (co2), r 180 pm at 30 °c and 120 kpa

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