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Zinc metal reacts with hydrochloric acid according to the balanced equation: zn(s) + 2 hcl(aq) ¡ zncl2(aq) + h2( g) when 0.103 g of zn(s) is combined with enough hcl to make 50.0 ml of solution in a coffee-cup calorimeter, all of the zinc reacts, raising the temperature of the solution from 22.5 °c to 23.7 °c. find ∆hrxn for this reaction as written. (use 1.0 g/ml for the

Respuesta :

Volume of solution is 50 mL and density is 1 g/mL thus, mass can be calculated as follows:

m=V×d

Putting the values,

m= 50 mL× 1 g/mL=50 g

Now, heat released by reaction is equal to heat absorbed thus, heat released can be calculated as follows:

[tex]Heat=m\times SH\times \Delta T[/tex]

Here, SH is specific heat, m is mass and [tex]\Delta T[/tex] is change in temperature.

Specific heat of water is 4.18 J/g°C, putting the values,

[tex]Heat=50 g\times 4.18 J/g°C\times \Delta (23.7 °C-22.5°C)=250.8 J[/tex]

Now, mass of zinc is 0.103 g and molar mass is 65.41 g/mol thus, number of moles of zinc can be calculated as:

[tex]n=\frac{m}{M}=\frac{0.103 g}{65.41 g/mol}=0.00157 mol[/tex]

Thus, [tex]\Delta H_{rxn}=\frac{Heat}{n}[/tex]

Putting the values,

[tex]\Delta H_{rxn}=\frac{(250.8 J)}{(0.00157 mol)}=1.6\times 10^{5} J/mol[/tex]

Therefore, [tex]\Delta H_{rxn}[/tex] for the given reaction is [tex]1.6\times 10^{5} J/mol[/tex]

Zinc metal reacts with hydrochloric acid to form zinc chloride and release hydrogen gas. The equation is exothermic, therefore, the change in enthalpy will be negative. The equation is:

[tex]\text {Zn}_{(s)} + 2 \text {HCl}_{(aq)} \rightarrow \text {ZnCl}_2_{(aq)} + \text {H}_{2}_{( g)}[/tex]

Given that,

  • Volume of solution = 50 mL
  • Density is = 1g/mL
  • Mass = Volume X density = 50 X 1 = 50 g

Now, the heat released by reaction is equal to the heat absorbed. The heat evolved can be measured as:

Heat = m X SH X [tex]\Delta[/tex] T,

where,

  • SH = Specific heat
  • m = mass
  • [tex]\Delta[/tex] T = Change in temperature

As water have specific heat of 4.18 J/g°C, substituting in the equation, it becomes:

  • [tex]\text {Heat} &= 50 \times 4.18 \text {J/g} ^{0}\text{C}\times \Delta (23.7^{0} \text C) - (22.5^{0} \text C)\\\text{Heat} &= 250.8\; \text J[/tex]

Also, the mass of zinc is given that 0.103 g and molar mass is 65.41 g/mol. Then, number of moles in zinc will be:

  • [tex]\text n &=\dfrac{m}{M}&=\dfrac{0.103 \;\text g}{65.41 \;\text{g/mol}}&=0.00157 \;\text{moles}[/tex]

Thus, enthalpy change will be:

  • [tex]\Delta \text H_{\text {rxn}}&=\dfrac{\text {Heat}}{\text n}[/tex]
  • [tex]\Delta \text H_{\text {rxn}}=\dfrac{250.8 \;\text J}{0.00157 \;\text{g/mol}}&= 1.6\times10^{5}\;\text{J/moles}[/tex]

Therefore, the [tex]\Delta \text H_{\text {rxn}}[/tex] = [tex]1.6\times10^{5}\;\text{J/moles}[/tex] for the given equation.

To know more about enthalpy change, refer to the following link:

https://brainly.com/question/13751788?referrer=searchResults

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