Respuesta :
Explanation:
[tex]2Cr +2H_3PO_4\rightarrow 3H_2 + 2CrPO_4[/tex]
a) First we will calculate moles of phosphoric acid present in 118.5 mL of a 0.8775 M solution.
[tex]Concentration=\frac{\text{Moles of compound}}{\text{Volume of the solution in L}}[/tex]
After determining the moles of phosphoric acid, we will then calculate the number pf moles of hydrogen gas by the help unitary method.
From moles of hydrogen gas mass of the hydrogen gas can be calculated easily by the formula:
=Moles of compound × molecular mass of compound
b) Moles of phosphoric acid in in 118.5 mL of a 0.8775 M solution be n
[tex]0.8775 M=\frac{n}{0.1885 L}[/tex]
n = 0.10398 mol
According to reaction , 2 moles of phosphoric acid gives 3 moles of hydrogen gas:
Then 0.10398 moles of phosphoric acid will give:
[tex]\frac{3}{2}\times 0.10398 mol=0.15597 mol[/tex] of hydrogen gas
0.15597 moles of hydrogen gas are produced.
Mass 0.15597 moles of hydrogen gas:
0.15597 mol × 2 g/mol=0.31194 g
0.31194 grams of hydrogen gas are produced.
Moles is the mass with respect to the molar mass of the substance or the compound. The moles of hydrogen produced is 0.155 moles and the mass is 0.3119 gm.
What are mass and moles?
Moles is the ratio of the mass of the substance with respect to the molar mass of the substance. While mass is the amount or the quantity of the substance present.
The reaction can be shown as,
[tex]\rm 2\;Cr + 2\; H_{3}PO_{4} \rightarrow 3\;H_{2} + 2\; CrPO_{4}[/tex]
Calculate the moles of the phosphoric acid present by the formula as:
[tex]\rm Concentration = \dfrac{Moles}{\text{volume of solution in L}}[/tex]
After the estimation of the moles of the phosphoric acid, the moles of hydrogen gas is estimated by the unitary method.
After estimating moles of hydrogen gas the mass of the gas can be estimated by the formula:
[tex]\rm mass = moles \times molar \;mass[/tex]
Calculation of the number of moles of phosphoric acid:
[tex]\begin{aligned}\rm 0.8775 \;\rm M &= \dfrac{\rm n}{0.1885\;\rm L}\\\\\rm n &= 0.103 \;\rm moles\end{aligned}[/tex]
Calculation of moles of hydrogen gas: [tex]\drac{3}{2}\times 0.1039 = 0.1559\;\rm moles[/tex]
Calculation of mass of hydrogen gas produced:
[tex]\begin{aligned}\rm mass &= 0.155 \times 2\\\\&= 0.3119\;\rm gm\end{aligned}[/tex]
Therefore, moles of hydrogen gas is 0.155 moles and mass is 0.3114 gms.
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