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3 years ago

What causes the emission of radiant energy that produces characteristic spectral lines for a given element?

Chemistry

2 answers:

Anarel [89]3 years ago

6 0

Answer:

When electrons move from a higher energy level to a lower one, photons are emitted, and an emission line can be seen in the spectrum. Absorption lines are seen when electrons absorb photons and move to higher energy levels. ... An atom in its lowest energy level is in the ground state.

Elis [28]3 years ago

5 0

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Chlorine can be prepared in the laboratory by the reaction of manganese dioxide with hydrochloric acid, HCl(aq)HCl(aq) , as desc

LekaFEV [45]

Answer:

1.131g of MnO2

Explanation:

Step 1:

The balanced equation for the reaction.

MnO2(s) + 4HCl(aq)—> MnCl2(aq) + 2H2O(l) + Cl2(g)

Step 2:

Data obtained from the question. This includes:

Volume (V) of Cl2 = 295mL = 0.295L

Temperature (T) = 25°C = 25°C + 273 = 298K

Pressure (P) = 795 Torr = 795/760 = 1.05 atm

Number of mole (n) of Cl2 =.?

Gas constant (R) = 0.082atm.L/Kmol

Step 3:

Determination of the number of mole of Cl2 produced. The number of mole of Cl2 produced from the reaction can be obtained by applying the ideal gas equation as follow:

PV = nRT

1.05 x 0.295 = n x 0.082 x 298

Divide both side by 0.082 x 298

n = (1.05 x 0.295)/(0.082 x 298)

n = 0.013 mole.

Therefore, the number of mole of Cl2 produced is 0.013 mole.

Step 4:

Determination of number of mole of MnO2 needed to produce 0.013 mole of Cl2.

This is illustrated below:

From the balanced equation above,

1 mole of MnO2 produced 1 mole of Cl2.

Therefore, it will also take 0.013 mole of MnO2 to produce 0.013 mole of Cl2.

Step 5:

Converting 0.013 mole of MnO2 to grams. This is illustrated below:

Number of mole MnO2 = 0.013 mole

Molar Mass of MnO2 = 55 + (2x16) = 87g/mol

Mass of MnO2 =?

Mass = number of mole x molar Mass

Mass of MnO2 = 0.013 x 87

Mass of MnO2 = 1.131g

Therefore 1.131g of MnO2 should be added to excess HCl.

4 0

3 years ago

Which material does not melt at any temperature?

lord [1]

Answer: Option (c) is the correct answer.

Explanation:

Wood is a mixture of different substances. Primarily it consists of cellulose, lignin, water etc.

When we heat wood then all these substance oxidize into the atmosphere even before they could melt.

Whereas iron, sodium chloride and ethanol all are the substances which can melt at any temperature.

Thus, we can conclude that out of the given options, wood, a mixture of different substances is a material that does not melt at any temperature.

6 0

3 years ago

The density of wind-packed snow is estimated to be 0.35 g/cm^3. A flat roof that is 35 by 43 feet has 28 inches of snow on it. H

xz_007 [3.2K]

Answer:

There are 76728.2 pounds of snow on the roof

Explanation:

To determine how many pounds of snow are on the roof,

First we will determine the mass of the snow in grams.

From the question,

Density of snow = 0.35 g/cm³

From

Density = Mass / Volume

To determine the mass, we will first find the volume.

From the question, a flat roof that is 35 by 43 feet has 28 inches of snow on it, that is, the height of the snow on the roof is 28 inches.

Area of the roof = 35 ft × 43 ft = 1505 ft²

Volume of the snow = Area of the roof × Height of the snow

Height of the snow = 28 inches

12 inches = 1 foot

∴ 28 inches = 28/12 feet = 2.3333 ft

Hence,

Volume of the snow = 1505 ft² × 2.3333 ft = 3511.62 ft³

Volume of the snow = 3511.62 ft³

This is the volume of the snow in cubic feet

Now, we will convert cubic feet (ft³) to cubic centimeter (cm³)

1 ft = 30.48 cm

and 1 ft³ = 30.48³ cm³ = 28316.84659 cm³.

If 1 ft³ = 28316.84659 cm³

∴ 3511.62 ft³ will be 3511.62 × 28316.84659 cm³ = 99438004.83 cm³

Hence, Volume of snow = 99438004.83 cm³

Now, we can determine mass of snow in grams

From

Density = Mass / Volume

Mass = Density × Volume

Mass = 0.35 g/cm³ × 99438004.83 cm³

Mass = 34803301.69 g

Now, we will convert the mass from grams to pounds

1 pound = 453.592 grams

If 453.592 grams = 1 pound

Then, 34803301.69 g will be 34803301.69 / 453.592 pounds = 76728.2 pounds

Hence, there are 76728.2 pounds of snow on the roof.

6 0

3 years ago

Large objects that form dense gravity wells in space A. Galaxies B. Star C. Nebulae D. Black holes.

BigorU [14]

Answer:

D. Black Holes

Explanation:

Black holes are large objects that form dense gravity wells in space. Their gravitational pull is so strong that even light cannot escape it.

5 0

3 years ago

Read 2 more answers

3.544g of hydrogen gas contains

Free_Kalibri [48]

Answer:

1.772 mols

Explanation:

Because hydrogen exists as a diatomic molecule in gaseous state, that's (H2), so then it's molecular mass is 1 ×2= 2g/mol.

we can now calculate for the number of moles, so

n=m/Mr

n=3.544/2

n=1.772mols

4 0

3 years ago

What causes the emission of radiant energy that produces characteristic spectral lines for a given element?​

What causes the emission of radiant energy that produces characteristic spectral lines for a given element?