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4 years ago

Someone pls pls pls help me with this question.

Chemistry

1 answer:

Arisa [49]4 years ago

3 0

$\rm{\pink{\underline{\underline{\blue{REASON:-}}}}}$

⭐ Elements in which the last electron enters any one of the five d-oribitals of their respective penultimate shells are called as d-block elements .

⭐ But the last electron of Zn , Cd , Hg and Cn enters in the s-oribital of their respective ultimate shells rather than the d-oribitals of their respective penultimate shells . Therefore, these elements cannot be regarded as d-block elements .

☃️ But properties of these elements resemble to the d-block elements rather than s-block elements .

☃️ Therefore, to make the study of periodic classification of elements more rational, they are studied along with d-block elements .

✍️ Thus on the basis of properties all transition elements are d- block elements, but on the basis of electronic configuration all d -block elements are not transition elements .

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iren2701 [21]

Answer:

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2) $Q_{rxn}=4435.04J$

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Explanation:

Hello there!

1) In this case, for these calorimetry problems, we can realize that since the temperature decreases the reaction is endothermic because it is absorbing heat from the solution, that is why the temperature goes from 22.00 °C to 16.0°C.

2) Now, for the total heat released by the reaction, we first need to assume that all of it is released by the solution since it is possible to assume that the calorimeter is perfectly isolated. In such a way, it is also valid to assume that the specific heat of the solution is 4.184 J/(g°C) as it is mostly water, therefore, the heat released by the reaction is:

$Q_{rxn}=-(15.0g+250.0g)*4.184\frac{J}{g\°C}(16.0-20.0)\°C\\\\ Q_{rxn}=4435.04J$

3) Finally, since the enthalpy of reaction is calculated by dividing the heat released by the reaction over the moles of the solute, in this case NH4Cl, we proceed as follows:

$\Delta _rH=\frac{ Q_{rxn}}{n}\\\\\Delta _rH= \frac{ 4435.04J}{15.0g*\frac{1mol}{53.49g} } *\frac{1kJ}{1000J} \\\\\Delta _rH=15.8kJ/mol$

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