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serious [3.7K]
3 years ago
15

4. A student started with a 0.032 g sample of copper which he took through the series of reactions described in this experiment.

At the end of the experiment he obtained 0.038 g of a black product. What was his percent yield
Chemistry
1 answer:
Elodia [21]3 years ago
6 0

Answer:

Y=48.6\%

Explanation:

Hello,

In this case, we can consider the following chemical reaction for the oxidation of copper which only occurs at high temperatures:

2Cu+O_2\rightarrow 2CuO

In such a way, for 0.032 grams of copper, the following grams of copper (II) oxide (black product) are yielded:

m_{CuO}=0.032gCu*\frac{1molCu}{63.546gCu} *\frac{2molCuO}{2molCu}*\frac{79.546gCuO}{1molCuO}  =0.078gCuO

Therefore, the percent yield is:

Y=\frac{0.038g}{0.078g}*100\%\\ \\Y=48.6\%

Best regards.

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The table shows the amount of radioactive element remaining in a sample over a period of time.
Assoli18 [71]

It would take 147 hours for 320 g of the sample to decay to 2.5 grams from the information provided.

Radioactivity refers to the decay of a nucleus leading to the spontaneous emission of radiation. The half life of a radioactive nucleus refers to the time required for the nucleus to decay to half of its initial amount.

Looking at the table, we can see that the initial mass of radioactive material present is 186 grams, within 21 hours, the radioactive substance decayed to half of its initial mass (93 g). Hence, the half life is 21 hours.

Using the formula;

k = 0.693/t1/2

k = 0.693/21 hours = 0.033 hr-1

Using;

N=Noe^-kt

N = mass of radioactive sample at time t

No = mass of radioactive sample initially present

k = decay constant

t = time taken

Substituting values;

2.5/320= e^- 0.033 t

0.0078 = e^- 0.033 t

ln (0.0078) = 0.033 t

t = ln (0.0078)/-0.033

t = 147 hours

Learn more: brainly.com/question/6111443

7 0
2 years ago
Positive ions from a base and negative ions from an acid form a_____ .
lara31 [8.8K]
They will form a Salt
5 0
3 years ago
Read 2 more answers
The acid dissociation constant Ka of boric acid (H3BO3) is 5.8 times 10^-10. Calculate the pH of a 4.4 M solution of boric acid.
madam [21]

Answer: The pH of a 4.4 M solution of boric acid is 4.3

Explanation:

H_3BO_3\rightarrow H^+H_2BO_3^-

at t=0  cM              0             0

at eqm c-c\alpha        c\alpha          c\alpha  

So dissociation constant will be:

K_a=\frac{(c\alpha)^{2}}{c-c\alpha}

Give c= 4.4 M and \alpha = ?

K_a=5.8\times 10^{-10}

Putting in the values we get:

5.8\times 10^{-10}=\frac{(4.4\times \alpha)^2}{(4.4-4.4\times \alpha)}

(\alpha)=0.000011

[H^+]=c\times \alpha

[H^+]=4.4\times 0.000011=4.8\times 10^{-5}M

Also pH=-log[H^+]

pH=-log[4.8\times 10^{-5}]=4.3

Thus pH of a 4.4 M H_3BO_3 solution is 4.3

3 0
3 years ago
You carefully weigh out 20.00 g of CaCO3 powder and add it to 81.00 g of HCl solution. You notice bubbles as a reaction takes pl
Zepler [3.9K]

Answer:

The relevant equation is:

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

Explanation:

1 mol of calcium carbonate can react to 2 moles of Hydrochloric acid to produce 1 mol of water, 1 mol of calcium chloride and 1 mol of carbon dioxide.

The formed CO₂ is the reason why you noticed bubbles as the reaction took place

3 0
3 years ago
A student experimentally obtained the density of osmium the densest element as 22.57g/cm3 the density of osmium is reported to b
Airida [17]

Answer:

The answer to your question is: % error = 0.4

Explanation:

Data

real value = 22.48%

estimated value = 22.57 %

Formula

% error = |real value - estimated value|/real value x 100

%error = |22.48 - 22.57|/22.48 x 100

% error = |-0.09|/22.48 x 100

%error = 0.09/22.48 x 100

% error = 0.004 x 100

% error = 0.4

3 0
3 years ago
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