Why should you cover the container during chromatography?

The correct answer is:

C. valence.

Explanation:

The valence or valency of an element is a stratagem of its connecting power with other atoms when it makes chemical compounds or molecules.

A valence electron is an outer shell electron that is connected with an atom, and that can compete in the formation of a chemical bond if the outer shell is not closed; in a single covalent bond, both atoms in the bond provide one valence electron in order to form a shared pair

Answer:

C. valence

Explanation:

The valence or valency of an element is a stratagem of its connecting power with other atoms when it makes chemical compounds or molecules.

A valence electron is an outer shell electron that is connected with an atom, and that can compete in the formation of a chemical bond if the outer shell is not closed; in a single covalent bond, both atoms in the bond provide one valence electron in order to form a shared pair.

Answer:

- The structural formula for Freon-12 (CCl2F2)

      F

       |

Cl - C - Cl

       |

      F

It has the same structure as methane (CH4) with Hydrogen atoms replaced by Chlorine and Fluorine

- Freon-12 and Freon-14 belong halocarbons, a compound in which the Hydrogen of a hydrocarbon is replaced by halogens, like Chlorine and Fluorine.

Answer:

Mole fraction = 0,0166

Explanation:

Mole fraction is defined as mole of a compound per total moles of the mixture. In the solution, the solute is fructose and the solvent is water. That means you need to find moles of fructose and moles of water.

The molecular mass of fructose is 180,16g/mol and mass of water is 18,02 g/mol. Using these values:

91,7g fructose × (1mol / 180,16g) = 0,509 moles of fructose

545g water × (1mol / 18,02g) = 30,24 moles of water

Thus, mole fraction of fructose is:

Mole fraction = 0,0166

I hope it helps!

Answer:

1) blue end of the spectrum

2) area of aperture

Explanation:

1) The electromagnetic spectrum encompases a wide range of frequency (ν) and wavelength (λ) that includes gamma rays, x-rays, ultra violet(UV), visible, infra red (IR), microwaves and radiowaves. The wavelength increases from gamma rays to radio waves.

The wavelength perceivable by human eyes lies in the UV-visible region which extends from 380 nm in the blue to 740 nm in the red.The shortest wavelengths occur in the blue end of the spectrum which also have the highest energy. In contrast, longer wavelengths occur on the red which have lower energy.

2) The light gathering capacity of a telescope is dependent upon its area of aperture. Larger the area, greater is the light gathering power which implies that the telescope has the capability of detecting weak or faint objects.

The area of the aperture is essentially the area of the objective of the telescopic lens which is given as:

where D = diameter of the lens

1) blue end of the spectrum

2) area of aperture

Answer:

(4) CH4

Explanation:

When there are no polar bonds in a molecule, there is no permanent charge difference between one part of the molecule and another, and the molecule is nonpolar.

In option A, HCl is not nonpolar because Cl has a pretty high electronegativity of 3.16, the H-Cl bond is polar due to the electronegative difference. This means option A is wrong.

In option B, A water molecule is polar because (1) its O-H bonds are significantly polar, and (2) its bent geometry makes the distribution of those polar bonds asymmetrical. The side of the water molecule containing the more electronegative oxygen atom is partially negative, and the side of the molecule containing the less electronegative hydrogen atoms is partially positive.

In option C, NH3 is polar because it has 3 dipoles that do not cancel out. Each N-H bond is polar because N is more electronegative than H. NH3 is overall asymmetrical in its VSEPR shape, so the dipoles don't cancel out and it is therefore polar.

In option D, CH4 looks like a C in the middle with 4 H's coming off of it. It is nonpolar because the electronegative difference is balanced. The H's all have the same electronegativities, and all cancel out since they are opposite one another.