Respuesta :
Answer:
6.46 grams (rounded to 3 sig. fig.)
Explanation:
The Theoretical Yield is calculated from the amount of reactants that are available. The value of the theoretical yield is independent of the actual yield.
This reaction involves two reactants:
- [tex]\rm H_2[/tex] and
- [tex]\rm N_2[/tex].
This question stated the mass of both. Start by determining which of the two is the limiting reactant.
Relative atomic mass data from a modern periodic table:
- H: 1.008;
- N: 14.007.
(1)
Assume that [tex]\rm H_2[/tex] is the limiting reactant. How many moles of [tex]\rm NH_3[/tex] will be produced?
[tex]M(\mathrm{H_2}) = 2\times 1.008 = \rm 2.016\; g\cdot mol^{-1}[/tex].
[tex]\begin{aligned} n(\mathrm{H_2}) &= \frac{m}{M}\\ &= \rm \frac{1.15\; g}{2.016\; g\cdot mol^{-1}}\\&\approx \rm 0.570437\; mol \end{aligned}[/tex].
Look up the coefficient ratio between [tex]\rm H_2[/tex] and [tex]\rm NH_3[/tex] in the balanced equation:
[tex]\displaystyle \frac{n(\mathrm{NH_3})}{n(\mathrm{H_2})} = \frac{2}{3}[/tex].
[tex]\begin{aligned} \frac{n(\mathrm{NH_3})}{n(\mathrm{H_2})}\cdot {n(\mathrm{H_2})} &= \frac{2}{3}\times \rm 0.570437\; mol \\&\approx \rm 0.380291\; mol\end{aligned}[/tex].
In other words, if [tex]\rm H_2[/tex] is the limiting reactant, approximately [tex]\rm 0.380291\; mol[/tex] of [tex]\rm NH_3[/tex] will be produced.
(2)
Similarly, assume that [tex]\rm N_2[/tex] is the limiting reactant. How many moles of [tex]\rm NH_3[/tex] will be produced?
[tex]M(\mathrm{N_2}) = 2\times 14.007 = \rm 28.014\; g\cdot mol^{-1}[/tex].
[tex]\begin{aligned} n(\mathrm{N_2}) &= \frac{m}{M}\\ &= \rm \frac{9.93\; g}{28.014\; g\cdot mol^{-1}}\\&\approx \rm 0.354466\; mol \end{aligned}[/tex].
Look up the coefficient ratio between [tex]\rm N_2[/tex] and [tex]\rm NH_3[/tex] in the balanced equation:
[tex]\displaystyle \frac{n(\mathrm{NH_3})}{n(\mathrm{N_2})} = 2[/tex].
[tex]\begin{aligned} \frac{n(\mathrm{NH_3})}{n(\mathrm{N_2})}\cdot {n(\mathrm{N_2})} &= 2\times 0.354466\rm \; mol \\&\approx \rm 0.708931\; mol\end{aligned}[/tex].
In other words, if [tex]\rm N_2[/tex] is the limiting reactant, approximately [tex]\rm 0.708931\; mol[/tex] of [tex]\rm NH_3[/tex] will be produced.
In theory, only around [tex]\rm 0.570437\; mol[/tex] of [tex]\rm NH_3[/tex] will be produced. The reaction will run out of [tex]\rm H_2[/tex] before all [tex]\rm N_2[/tex] are consumed.
The mass of that much [tex]\rm NH_3[/tex] is approximately 6.46 grams.
The theoretical yield of the reaction is 6.51 g of ammonia.
The equation of the reaction is; 3H2(g)+N2(g)→2NH3(g)
Number of moles of H2 = 1.15 g/2 g/mol = 0.575 moles
Number of moles of N2 = 9.93 g/28 g/mol = 0.355 mole
We need to find the limiting reactant which is the reactant that yields the least amount of product.
Given that;
3 moles of H2 yields 2 moles of ammonia
0.575 moles of H2 yields 0.575 moles × 2 moles/3 moles
= 0.383 moles of ammonia
Also;
1 mole of N2 yields 2 moles of ammonia
0.355 mole of N2 yields 0.355 mole× 2 moles/ 1 mole of N2
= 0.71 moles of ammonia
The limiting reactant is hydrogen.
Theoretical yield of ammonia = 0.383 moles of ammonia × 17 g/mol = 6.51 g of ammonia
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