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siniylev [52]
3 years ago
5

6.7 mL of a ptassium chlorid solution was added to a 54.730 gevaporating dish. The combination weight 61.945 g. Afterevaporation

the dish contents weight 55.428 g.
a. What was the mass percent of potassium chloride in thesolution?
b. If the actual mass percent of the potassium in the abovesolution was 10.00%, what was the percentage error of the abovemeasurment?
c. Why was the evaporation used to determine the masspercentage of potassium cloride in the solution rather than thefiltration or recrystallization? Explain.
Chemistry
1 answer:
Semmy [17]3 years ago
3 0

Explanation:

A.

Mass of evaporation dish + solution of KCl = mass of dish + mass of solution of KCl

61.945 = 54.73 + mass of KCl solution

= 7.215 g

Mass of evaporation dish + dry KCl = mass of dish + mass of dry KCl

55.428 = 54.73 + mass of dry KCl

= 0.698 g.

% Mass of KCl = mass of dry KCl/mass of KCl solution * 100

= 0.698/7.215 * 100

= 9.67%

B.

At 10%, mass = 0.7215 g

Change in error = 0.7215 - 0.698

= 0.0235 g

% error = change in error/actual mass at 10% * 100

= 0.0235/0.7215 * 100

= 3.26 %

C.

In evaporation, KCl does not decompose on heating. In filtration, there needs to be a heterogeneous solution(particles or suspension of KCl present) and it is not suitable for soluble salts while recrystallisation is mainly a purification process for solution and KCl is equally soluble in cold and hot water.

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Answer:

Explanation:

  • For the balanced reaction:

<em>4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)​.</em>

It is clear that 4 mol of Fe react with 3 mol of O₂ to produce 2 mol of Fe₂O₃.

  • Firstly, we need to calculate the no. of moles of 35.8 grams of Fe metal:

no. of moles of Fe = mass/molar mass = (35.8 g)/(55.845 g/mol) = 0.64 mol.

  • Now, we can find the no. of moles of O₂ is needed to react with the proposed amount of Fe:

<em><u>Using cross multiplication:</u></em>

4 mol of Fe is needed to react with → 3 mol of O₂, from stichiometry.

0.64 mol of Fe is needed to react with → ??? mol of O₂.

∴ The no. of moles of O₂ needed = (3 mol)(0.64 mol)/(4 mol) = 0.48 mol.

  • Finally, we can get the volume of oxygen using the information:

<em>It is known that 1 mole of any gas occupies 22.4 L at standard P and T (STP).</em>

<em></em>

<em><u>Using cross multiplication:</u></em>

1 mol of O₂ occupies → 22.4 L, at STP conditions.

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5 0
3 years ago
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○ c. ○

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The structure of the alkyl bromides used in a malonic ester synthesis of ethyl 2-methyl-4-pentenoate are as drawn in the attached image.

<h3>Ethyl 2-methyl-4-pentenoate by Malonic ester synthesis.</h3>

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Hence, it follows from the structure of Ethyl 2-methyl-4-pentenoate that the alkyl bromides used are Ethyl bromide and methyl bromide.

Read more on Malonic ester synthesis;

brainly.com/question/17237043

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The reaction of NaClO₄ is:

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For HNO₂ equilibrium is:

HNO₂ ⇄ H⁺ + NO₂⁻

k = [H⁺] [NO₂⁻] / [HNO₂] = 4,5x10⁻⁴

As k value is higher for HNO₂, the concentration of H⁺ will be higher in this system doing the HNO₂ with the lower pH.

f) 0.1 M HNO2

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