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DerKrebs [107]
3 years ago
10

What is the wavelength of radio waves? Which statement is true for a cooling curve? A. It shows how the temperature of the subst

ance falls as heat is removed. B. It shows how the temperature of the substance changes when heat is applied. C. It shows the increase in the average kinetic energy of the particles. D. It shows how heat absorption affects the motion of particles. E. It shows how energy gain causes the temperature to fall.

Chemistry
1 answer:
ladessa [460]3 years ago
5 0

Answer:

Most radio waves have wavelengths between 1 mm and 100 km.

A cooling curve shows A. how the temperature of a substance falls as heat is removed.

Explanation:

<em>Radio waves</em> are the longest of all the waves in the electromagnetic spectrum.

Most have wavelengths between 1 mm and 100 km, although there is no upper limit.

Some radio waves have wavelengths of 10 000 km.

A <em>cooling curve</em> (see image below) shows how the temperature of a substance falls as it is cooled.

In Option E., a decrease in temperature would cause an energy <em>loss</em>.

Options B., C., and D. involve the <em>addition of heat</em>.

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a rock is found to have a small amount of copper would you call the rock an ore of copper explain in 5-6 sentences
alexgriva [62]

Answer:

Answer: No. An ore is a rock having large amounts of a mineral. Minerals may or may not be commercially useful.

3 0
3 years ago
Suppose a laboratory wants to identify an unknown pure substance. The valence electrons of the substance's atoms feel an effecti
zalisa [80]

Answer:

  • The answer is the third option in the list:<em> It would have smaller atomic radii than Si and higher ionization energies than Si.</em>

Explanation:

The<em> effective nuclear charge</em> is that portion of the total nuclear charge that a given electron in an atom feels.

Since, the inner electrons repel the outer electrons, t<em>he effective nuclear charg</em>e of a determined electron is the sum of the positive charge (number of protons or atomic number) that it feels from the nucleus less the number of electrons that are in the shells that are are closer to the nucleus than the own shell of such (determined) electron.

Mathematically, <em>the effective nuclear charge (Zeff)</em> is equal to the atomic number (Z) minus the amount (S) that other electrons in the atom shield the given (determined) atom from the nucleus.

  • Zeff = Z - S.

Since, the valence electrons are the electrons in the outermost shell of the atom, you can find certain trend for the value Zeff.

Let's look at the group to which Si belongs, which is the group 14. This table summarizes the relevant data:

Element   Z   Group   # valence electrons     S                      Zeff = Z - S

C              6      14                      4                     6 - 4 = 2             6 -  2 = +4

Si             14     14                      4                     14 - 4 = 10         14 - 10 = +4

Ge           32     14                     4                     32 - 4 = 28       32 -28 = +4

Sn           50     14                     4                     50 - 4 = 46       50 - 46 = +4

Pb           82     14                     4                     82 - 4 = 78        82 - 78 = +4  

With that, you have shown that the valence electrons of the unknown substance's atoms feel an effective nuclear charge of +4 and you have a short list of 4 elements which can be the unknown element: C, Ge, Sn or Pb.

The second known characteristic of the unknown substance's atoms is that it has a <em>higher electronegativity than silicon (Si)</em><em>.</em>

So, you must use the known trend of the electronegativity in a group of the periodic table: the electronegativity decreases as you go down in a group. So, three of the elements (Ge, Sn, and Pb) have lower electronegativity than Si, which has left us with only one possibility: the element C. The valence electrons of carbon (C) atoms feel an effective nuclear charge of +4 and it carbon has a higher electronegativity than silicon.

Other two periodic trends attending the group number are the <em>atomic radii and the ionization energy</em>.

The atomic radii generally increases as you go from top to bottom in a group. This is because you are adding electrons to new higher main energy levels. So, you can conclude that the originally unknwon substance (carbon) has a smaller atomic radii, than Si.

The ionization energies generally decreases as you go from top to bottom in a group. This os due to the shielding effect: as seen, the effective nuclear charge of the atom's valence electrons remains constant, while the distance of the electrons from the nucleus increases (the valence electrons are farther away from the nucleus), which means the upper the element in a given group, the larger the ionization energy of the atoms.

With this, our conclusions about the unnkown substance are:

  • Since it has a higher electronegativity value than silicon (Si), it is right up of Si, and there is on only element possible element than can be (C).

  • Since, it is upper than silicon (Si), it would have smaller atomic radii.

  • Due to the shielding effect, it would have larger ionization energies.

  • The answer is the third option in the list: It would have smaller atomic radii than Si and higher ionization energies than Si.

6 0
2 years ago
Are properties such as odor, color, density, and solubility physical or chemical properties?
storchak [24]
Physical properties- color, density, solubility.
<span>Chemical property- odor.

</span>You see, a physical property<span> is any property that can be </span>measured<span> , and a one that </span><span>describes the state of the physical system.
</span>
https://socratic.org/questions/are-properties-such-as-odor-color-density-and-solubility-physical-or-...
8 0
3 years ago
Read 2 more answers
Winter is coming and it's time to make sure you have the right amount of antifreeze
ololo11 [35]

The molality of the solution = 17.93 m

<h3>Further explanation</h3>

Given

6.00 L water with 6.00 L of  ethylene glycol(ρ=1.1132 g/cm³= 1.1132 kg/L)

Required

The molality

Solution

molality = mol of solute/ 1 kg solvent

mol of solute = mol of ethylene glycol

  • mass of ethylene glycol :

= volume x density

= 6 L x 1.1132 kg/L

= 6.6792 kg

= 6679.2 g

  • mol of ethylene glycol (MW=62.07 g/mol)

=mass : MW

=6679.2 : 62.07

=107.608

  • mass of water

6 L water = 6 kg water(ρ= 1 kg/L)

  • molality

\tt =\dfrac{107.608}{6}=17.93~m

5 0
2 years ago
What is the lewis dot structure of NaBr
Anon25 [30]
<span><span>LiF, LiCl, LiBr, LiI, LiAtNaF, NaCl, NaBr, NaI, NaAtKF, KCl, KBr, KI, KAt</span><span>RbF, RbCl, RbBr, RbI, RbAt CsF, CsCl, CsBr, CsI, CsAt FrF, FrCl, FrBr, FrI, FrAt<span>
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3 0
3 years ago
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