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Nezavi [6.7K]
3 years ago
9

Based on the periodic table, what do we now call the element mendeleev called eka-manganese?

Chemistry
2 answers:
myrzilka [38]3 years ago
8 0
Based on the periodic table, the element mendeleev called eka-manganese is now called technetium. Technetium<span> is a silvery-gray metal that tarnishes slowly in moist air. Hope this answers the question. Have a nice day. Feel free to ask more questions.</span>
Keith_Richards [23]3 years ago
6 0

Answer:

Technetium

Explanation:

The Mendeleev element called eka-manganese is now called Technetium.

Technetium is a crystalline, silver and radioactive metal, very similar to platinum. It serves as a gamma ray source of beta particles. Most of the technetium produced on Earth is a byproduct of uranium-235 fission in nuclear reactors and is extracted from nuclear fuel rods. No isotope of technetium has a half-life of more than 4.2 million years, so its detection in 1952 helped reinforce the theory that stars can produce heavier elements.

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A sample of gas with a mass of 21.3 g is confined to a vessel of volume 7.73 L at 0.880 atm and 30.00C.
rodikova [14]

Answer:

(a) 77.9 g/mol

(b) 3.18 g / L

Explanation:

<u>(a)</u> We need to use the ideal gas law, which states: PV = nRT, where P is the pressure, V is the volume, n is the moles, R is the gas constant, and T is the temperature in Kelvins.

Notice that we don't have moles; we instead have the mass. Remember, though that moles can be written as m/M, where m is the mass and M is the molar mass. So, we can replace n in the equation with m/M, or 21.3/M. The components we now have are:

- P: 0.880 atm

- V: 7.73 Litres

- n: m/M = 21.3 g / M

- R: 0.08206

- T: 30.00°C + 273 = 303 K

Plug these in:

PV = nRT

(0.880)(7.73) = (21.3/M)(0.08206)(303)

Solve for M:

M = 77.9 g/mol

<u>(b)</u> The equation for the molar mass is actually:

M = (dRT)/P, where d is the density

We have all the components except d, so plug them in:

77.9 = (d * 0.08206 * 298) / 1

Solve for d:

d = 3.18 g / L

3 0
3 years ago
Read 2 more answers
A student was provided with a solid sample made up of a mixture of components. Prior to separation, the student measured 2.895 g
Shtirlitz [24]

Answer:

Component 1, since it has the greatest mass.

Explanation:

Hello,

In this case, considering that the by-mass percent of a substance is computed:

\% m/m_i=\frac{m_i}{m_{mixture}}*100\%

In such a way, given the form of the equation one could infer that the higher the mass of the i component, the higher its by-mass percent, it means that the component with the greatest mass will have the highest by-mass percent for the mixture. In such a way, since the component 1 was found to have a mass of 1.12 g, it will have the highest by-mass percent.

Best regards.

7 0
3 years ago
What are two main purposes for using repetition when conducting experiments <br> irements
Sloan [31]
To reduce mistakes and save time
4 0
3 years ago
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A 1.00 g sample of naphthalene (C10H8) contains 0.562 g of hydrogen. What is the mass percent of carbon in the compound?
chubhunter [2.5K]

Answer:

mass of carbon = 0.438g

Explanation:

mass percentage = 0.00438%

6 0
3 years ago
Magnesium reacts with hydrochloric acid, HCl, to form magnesium chloride and hydrogen gas. The reaction is: Mg + 2HCl → MgCl2 +
prisoha [69]
Answer is: mass of HCl is 15,6 g.
Chemical reaction: Mg + 2HCl → MgCl₂ + H₂.
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n(Mg) = m(Mg) ÷ M(Mg).
n(Mg) = 5,2 g ÷ 24,3 g/mol.
n(Mg) = 0,213 mol.
From chemical reaction: n(Mg) : n(HCl) = 1 : 2.
n(HCl) = 0,426 mol.
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m(HCl) = 15,6 g.
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