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3 years ago

The Russian chemist who designed the periodic table that was similar to the Periodic Table used today was _______________-

1 answer:

8 0

Dmitri Mendeleev, he realized that the physical and chemical properties of elements were related to their atomic mass and arranged them into groups (columns)

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As part of a soil analysis on a plot of land, a scientist wants to determine the ammonium content using gravimetric analysis wit

jeka94

Answer:

Mass percentage of NH₄Cl = 3.54%

Mass percentage of K₂CO₃ = 1.01%

Explanation:

If a 200.0 mL aliquot produced 0.105 g of KB(C₆H₅)₄, then a 100.0 mL aliquot would produce 1/2 * 0.105 g = 0.0525 g of KB(C₆H₅)₄.

Therefore, mass of NH₄B(C₆H₅)₄ in the 100.0 ml aliquot = (0.277 - 0.0525)g = 0.2245 g

Number of moles of NH₄B(C₆H₅)₄ in 0.2245 g = 0.2245 g/ 337.27 g/mol = 0.0006656 moles

In 500 ml solution, number of moles present = 0.0006656 * 500/100 = 0.003328 moles.

From equation of the reaction; mole ratio of NH₄⁺ and NH₄B(C₆H₅)₄ = 1:1

Similarly, mole ratio of NH₄⁺ and NH₄Cl = 1:1

Therefore, moles of NH₄Cl in 500 ml sample = 0.003328 moles

Mass of NH₄Cl = 0.003328 mol * 53.492 g/mol = 0.178 g

Mass percentage of NH₄Cl = (0.178/5.025) * 100% = 3.54%

Number of moles of KB(C₆H₅)₄ in 0.105 g (precipitated from 200.0 ml aliquot) = 0.105 g/ 358.33 g/mol = 0.000293 moles

In 500 ml solution, number of moles present = 0.000293 * 500/200 = 0.0007326 moles.

From equation of the reaction; mole ratio of K⁺ and KB(C₆H₅)₄ = 1:1

Similarly, mole ratio of K⁺ and K₂CO₃ = 2:1

Therefore, moles of K₂CO₃ in 500 ml sample = 0.0007326/2 moles = 0.0003663 moles

Mass of K₂CO₃ = 0.0003663 mol * 138.21 g/mol = 0.05063 g

Mass percentage of K₂CO₃ = (0.05063/5.025) * 100% = 1.01%

7 0

3 years ago

Chemistry help!<br><br>Zoom in to see better!!

inna [77]

Answer:

11.9 g of nitrogen monoxide

Explanation:

We'll begin by calculating the number of mole in 6.75 g of NH₃. This can be obtained as follow:

Mass of NH₃ = 6.75 g

Molar mass of NH₃ = 14 + (3×1)

= 14 + 3

= 17 g/mol

Mole of NH₃ =?

Mole = mass /molar mass

Mole of NH₃ = 6.75 / 17

Mole of NH₃ = 0.397 mole

Next, we shall determine the number of mole of NO produced by the reaction of 0.397 mole of NH₃. This can be obtained as follow:

4NH₃ + 5O₂ —> 4NO + 6H₂O

From the balanced equation above,

4 moles of NH₃ reacted to produce 4 moles of NO.

Therefore, 0.397 mole of NH₃ will also react to produce 0.397 mole of NO.

Finally, we shall determine the mass of 0.397 mole of NO. This can be obtained as follow:

Mole of NO = 0.397 mole

Molar mass of NO = 14 + 16 = 30 g/mol

Mass of NO =?

Mass = mole × molar mass

Mass of NO = 0.397 × 30

Mass of NO = 11.9 g

Thus, the mass of NO produced is 11.9 g

7 0

2 years ago

What is the concentration of the barium hydroxide solution if 50.0 mL of a 0.425 M HNO3 solution is required to neutralize a 36.

fomenos

The molarity of Barium Hydroxide is 0.289 M.

<u>Explanation:</u>

We have to write the balanced equation as,

Ba(OH)₂ + 2 HNO₃ → Ba(NO₃)₂ + 2 H₂O

We need 2 moles of nitric acid to react with a mole of Barium hydroxide, so we can write the law of volumetric analysis as,

V1M1 = 2 V2M2

Here V1 and M1 are the volume and molarity of nitric acid

V2 and M2 are the volume and molarity of Barium hydroxide.

So the molarity of Ba(OH)₂, can be found as,

$$ M2 = \frac{V1 \times M1}{2 \times V2}$

$$M2 = \frac{50 \times 0.425 }{2 \times 36.8}$

= 0.289 M

5 0

3 years ago

A scientist, Dr. Sigma, states that a chemical taken internally once a day will prevent the common cold. However, no other scien

pshichka [43]

Answer:

not valid

Explanation:

Expert judgment is a useful validation method to verify the reliability of an investigation that is defined as “an informed opinion of people with experience in the subject, who are recognized by others as qualified experts in it, and who can give information, evidence, judgments and assessments ”

After submitting an instrument for comparison to the consultation and expert opinion, it must meet two quality criteria: validity and reliability. The validity of content is often established based on two situations, one that concerns the design of a test and the other, the validation of an instrument subject to translation and standardization procedures to adapt it to different cultural meanings. It is here that the task of the expert becomes a fundamental task to eliminate irrelevant aspects, incorporate those that are essential and / or modify those that require it.

5 0

3 years ago

Given this equation: 3 MgCl2 + 2 AL - 3 Mg + 2 AlCl3, if 278 grams of magnesium chloride

netineya [11]

Answer: m= 1.02x10² g AlCl3 or 1091.3 g AlCl3

Explanation: solution attached.

Convert mass of Mg to moles

Do the mole ratio between Mg and AlCl3 based from the balanced equation.

Convert moles of AlCl3 to mass using its molar mass.

6 0

3 years ago