C. Distance from Earth
The observed brightness of a star (the apparent magnitude) to an absolute magnitude, you need to know the distance [d], to the star. Alternatively, if we know the distance and the apparent magnitude [m] of a star, we can calculate its absolute magnitude [d].
*paraphrased from "COSMOS.com"
<u>Hydrogen bonds </u>are weak bonds that are not strong enough to hold atoms together to form molecules but are strong enough to form bonds within and around large molecules.
- The hydrogen bond is weak bond.
- The hydrogen bond is electrostatic force of attraction between hydrogen atom and more electronegative atoms or group ( like Florine , oxygen or nitrogen) which is contently bonded.
- The hydrogen bond is occur in polar , contently bond atoms in different molecules.
- Example is H-O-H or

- The positively charged hydrogen side of one water molecule is bond with negatively charged oxygen side of another molecule.
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Answer:Answer: The step that is NOT necessary to complete before a cuvette is placed into the spectrophotometer is option B (Write, in ink, either sample or blank on the side of the cuvette to keep track of them)
Explanation: spectrophotometer is an instrument used to measure the light intensity absorbed after being passed through a solution. Before the absorbance of the sample solution, a solvent solution called blank is used for the calibration of the machine and this blank solvent is placed in a cuvette. The procedure usually comes first before the main sample is processed. Therefore there is no need to
Write, in ink, either sample or blank on the side of the cuvette to keep track of them. This is so since sample and blank is not absorbed at the same time by the machine.
<u>Answer:</u> The molar solubility of
is 
<u>Explanation:</u>
Solubility is defined as the maximum amount of solute that can be dissolved in a solvent at equilibrium.
Solubility product is defined as the product of concentration of ions present in a solution each raised to the power its stoichiometric ratio.
The balanced equilibrium reaction for the ionization of calcium fluoride follows:

s 2s
The expression for solubility constant for this reaction will be:
![K_{sp}=[Pb^{2+}][I^-]^2](https://tex.z-dn.net/?f=K_%7Bsp%7D%3D%5BPb%5E%7B2%2B%7D%5D%5BI%5E-%5D%5E2)
We are given:

Putting values in above equation, we get:

Hence, the molar solubility of
is 
Answer:Scientific literacy is the knowledge and understanding of scientific concepts and processes required for personal decision making, participation in civic and cultural affairs, and economic productivity. It also includes specific types of abilities.Science literacy is important because it provides a context for addressing societal problems, and because a science- literate populace can better cope with many of its prob- lems and make intelligent and informed decisions that will affect the quality of their lives and those of their children.
Explanation: