QUESTION 20

If 9.8g water is used in electrolysis, what is the percent yield if 5.6g of oxygen was

ANEK [815]

Answer:

Approximately $64\%$ .

Explanation:

$\displaystyle \text{Percentage Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\%$

The actual yield of $\rm O_2$ was given. The theoretical yield needs to be calculated from the quantity of the reactant.

Balance the equation for the hydrolysis of water:

$\rm 2\, H_2O \, (l) \to 2\, H_2\, (g) + O_2\, (g)$ .

Note the ratio between the coefficient of $\rm H_2O\, (g)$ and $\rm O_2\, (g)$ :

$\displaystyle \frac{n(\mathrm{O_2\, (g)})}{n(\mathrm{H_2O\, (aq)})} = \frac{1}{2}$ .

This ratio will be useful for finding the theoretical yield of $\rm O_2\, (g)$ .

Look up the relative atomic mass of hydrogen and oxygen on a modern periodic table.

$\rm H$ : $1.008$ .
$\rm O$ : $15.999$ .

Calculate the formula mass of $\rm H_2O$ and $\rm O_2$ :

$M(\mathrm{H_2O}) =2\times 1.008 + 15.999 = 18.015\; \rm g \cdot mol^{-1}$ .

$M(\mathrm{O_2}) =2\times 15.999 = 31.998\; \rm g \cdot mol^{-1}$ .

Calculate the number of moles of molecules in $9.8\; \rm g$ of $\rm H_2O$ :

$\displaystyle n(\mathrm{H_2O}) = \frac{m(\mathrm{H_2O})}{M(\mathrm{H_2O})} = \frac{9.8\; \rm g}{18.015\; \rm g \cdot mol^{-1}} \approx 0.543991\;\rm g \cdot mol^{-1}$ .

Make use of the ratio $\displaystyle \frac{n(\mathrm{O_2\, (g)})}{n(\mathrm{H_2O\, (aq)})} = \frac{1}{2}$ to find the theoretical yield of $\rm O_2$ (in terms of number of moles of molecules.)

$\begin{aligned} n(\mathrm{O_2}) &= \displaystyle \frac{n(\mathrm{O_2\, (g)})}{n(\mathrm{H_2O\, (aq)})} \cdot n(\mathrm{H_2O}) \\ &\approx \frac{1}{2} \times 0.543991\; \rm mol \approx 0.271996\; \rm mol \end{aligned}$ .

Calculate the mass of that approximately $0.271996\; \rm mol$ of $\rm O_2$ (theoretical yield.)

$\begin{aligned}m(\mathrm{O_2}) &= n(\mathrm{O_2}) \cdot M(\mathrm{O_2}) \\ &\approx 0.271996\; \rm mol \times 31.998\; \rm g \cdot mol^{-1} \approx 8.70331 \; \rm g \end{aligned}$ .

That would correspond to the theoretical yield of $\rm O_2$ (in term of the mass of the product.)

Given that the actual yield is $5.6\; \rm g$ , calculate the percentage yield:

$\begin{aligned}\text{Percentage Yield} &= \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\% \\ &\approx \frac{5.6\; \rm g}{8.70331\; \rm g} \times 100\% \approx 64\%\end{aligned}$ .

4 0

2 years ago

HELP I DONT KNOW HOW TO DO THIS !!

BlackZzzverrR [31]

Answer:

you divide 71.5 by 2

Explanation:

it's may look intimidating but the question is actually really simple.

5 0

2 years ago

After creating a definition for what it means to be sexually abstinent, list reasons why being abstinent is important for you an

Sever21 [200]

Sexually abstinent: refraining from some or all sexual activities
school (higher education)
health (stds)
pregnancy (not ready for children)

5 0

3 years ago

The ka values for several weak acids are given below. which acid (and its conjugate base) would be the best buffer at ph = 8.0?

Pie

One of the best buffer choice for pH = 8.0 is Tris with Ka value of 6.3 x 10^-9.

To support this answer, we first calculate for the pKa value as the negative logarithm of the Ka value:
pKa = -log Ka

For Tris, which is an abbreviation for 2-Amino-2-hydroxymethyl-propane-1,3 -diol and has a Ka value of 6.3 x 10^-9, the pKa is
pKa = -log Ka
= -log (6.3x10^-9)
= 8.2

We know that buffers work best when pH is equal to pKa:
pKa = 8.2 = pH

Therefore Tris would be a best buffer at pH = 8.0.

7 0

3 years ago

Read 2 more answers

How many grams of sulfur are needed to react completely with 246 g of mercury to form hgs?

iren [92.7K]

The reaction between mercury (Hg) and sulfur (S) to form HgS is:

Hg + S ------------- HgS

Therefore: 1 mole of Hg reacts with 1 mole of S to form 1 mole of HgS

The given mass of Hg = 246 g

Atomic mass of Hg = 200.59 g/mol

# moles of Hg = 246 g/ 200.59 gmol-1 = 1.226 moles

Based on the reaction stoichiometry,

# moles of S that would react = 1.226 moles

Atomic mass of S = 32 g/mol

Therefore, mass of S = 1.226 moles*32 g/mole = 39.23 g

39.2 g of sulfur would be needed to react completely with 246 g of Hg to produce HgS

5 0

2 years ago

Read 2 more answers