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s344n2d4d5 [400]
3 years ago
11

Douglasite is a mineral with the formula 2KCl • FeCl2 • 2H2O. Calculate the mass percent of douglasite in a 455.0-mg sample

if it took 37.20 mL of a 0.1000 M AgNO3 solution to precipitate all the Cl2 as AgCl. Assume the douglasite is the only source of chloride ion.
Chemistry
1 answer:
Keith_Richards [23]3 years ago
3 0

Answer:

The mass percentage is 63.3%

Explanation:

First we need to know how much of the AgNO3 we are using to precipitate the chloride, for this we use:

(37.2 ml * 0.1 M)/1000 ml = 0.00372 moles of AgNO3 which means 0.00372 moles of silver.

the relation between Ag and Cl in the precipitation is 1:1, so we can determine that in our sample we have 0.00372 moles of Cl- and in grams we have 131 mg.

Now we need to know how much of the Douglasite is actually chloride. For that we calculate the molar mass:

Mr = 2*39 + 4*35.45 + 55.85 + 2*18 = 311.65 g/mole

Of that 311.65 grams, 141.8 are Cl. So we could calculate how much of the sample is actual Douglasite:

141.8 g Cl --> 311.65 g Douglasite

0.131 g Cl --> x  = 0.288 g douglasite.

The sample is 0.455 and represents 100 %

Then, the 288 mg of douglasite is the 63.3 %

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katen-ka-za [31]

Answer:

Ca²⁺ + 2 OH⁻ → Ca(OH)₂(s)

Explanation:

In chemistry, the net ionic equation is a way to write a chemical reaction whereas you write only the ions that are involved in the reaction.

When calcium chloride, CaCl₂ reacts with sodium hydroxide, NaOH to produce Ca(OH)₂ the only ions involved in the reaction are Ca²⁺ and OH⁻, thus, the balanced net ionic equation is:

<em>Ca²⁺ + 2 OH⁻ → Ca(OH)₂(s)</em>

<em>Cl⁻ and Na⁺ are not involved in the reaction and you don't have to write them.</em>

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1. How many molecules of S2 gas are in 756.2 L?
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Answer: There are 2.032 \times 10^{25} molecules S_{2} gas are in 756.2 L.

Explanation:

It is known that 1 mole of any gas equals 22.4 L at STP. Hence, number of  moles present in 756.2 L are calculated as follows.

Mole = \frac{Volume}{22.4 L}\\= \frac{756.2 L}{22.4 L}\\= 33.76 mol

According to mole concept, 1 mole of every substance contains 6.022 \times 10^{23} molecules.

Therefore, molecules of S present in 33.76 moles are calculated as follows.

1 mol = 6.022 \times 10^{23}\\33.76 mol = 33.76 \times 6.022 \times 10^{23}\\= 2.032 \times 10^{25}

Thus, we can conclude that there are 2.032 \times 10^{25} molecules S_{2} gas are in 756.2 L.

5 0
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A medical research lab in Europe is studying a drug’s absorption in the blood. Another lab in Japan is trying to delay the elimi
ladessa [460]

The correct answer is From different social and ethnic backgrounds.

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The purpose of science studies is to gain an understanding of specific phenomena and use this in the benefit of the world or humanity. Moreover, science is guided by objective methods and these are applied all around the world. This feature allows scientists from all kinds of social and ethnic backgrounds to study the same phenomena and obtain similar results, which is essential for the progress of scientific knowledge. This is exemplified by two different labs in two different countries studying drug absorption because the results of these two studies can be analyzed together to understand drug absorption.

In this context, one factor that contributes to the progress of scientific knowledge is the effort of scientists "from different social and ethnic backgrounds".

7 0
3 years ago
1 pts
bonufazy [111]

Answer:

secound one is the answer: Distillation

this may help you

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