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emmainna [20.7K]
4 years ago
9

What is the name of the phase where stars live out most of their lives?

Chemistry
1 answer:
lisov135 [29]4 years ago
8 0
The correct option is B. 
Stars live out most of their lives at MAIN SEQUENCE. Stars generally are divided into three major stages, these are:
1. Pro stars and pre-main sequence star
2. Main sequence  and giant star
3. Variable stars
Major stages in the life of a star can last for millions of years.

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A molecular biologist measures the mass of cofactor a in an average yeast cell. the mass is 41.5 pg . what is the total mass in
Hitman42 [59]
The unit pg stands for pictogram. It is one-trillionth of a gram. Because of the very small mass, it is expressed in the prefix form of the base units for convenience. Now, the mass of cofactor a is 41.5 pg per cell. Since there are a total of 105 cells, the total mass would be:

Total mass = 105 cells * 41.5 pg/cell = 4,357.5 pg 
6 0
3 years ago
as the elements period 3 are considered in order of increasing atomic number, the number of principal energy levels in each succ
Diano4ka-milaya [45]

Answer:

stay the same.

Explanation:  Period 3 consists of the full 1s, 2s, and 2p electron orbitals, plus the 3s and 3p valence orbitals, which are filled with a total of 8 more electrons as we move from left (Na) to the far right (Ar):

Na:  1s2 2s2 2p6 3s1

Ar:    s2 2s2 2p6 3s2 3p6

As we move from left to right, and ignoring the already-filled 1s, 2s, and 2p orbitals, the period three starting and ending elements have the following:

Na: 3s1

Ar: 3s2, 3p6

All the new electrons electrons filled the third energy level (3s and 3p).  So the energy level does not change, just the orbitals.

5 0
3 years ago
Calculate the mole fraction of kbr (molar mass 119.00 g/mol) in a solution made by dissolving 0.30 g kbr in 0.400 l of H2O (d =
julia-pushkina [17]

The mole fraction of KBr in the solution is 0.0001

<h3>How to determine the mole of water</h3>

We'll begin by calculating the mass of the water. This can be obtained as follow:

  • Volume of water = 0.4 L = 0.4 × 1000 = 400 mL
  • Density of water = 1 g/mL
  • Mass of water =?

Density = mass / volume

1 = Mass of water / 400

Croiss multiply

Mass of water = 1 × 400

Mass of water = 400 g

Finally, we shall determine the mole of the water

  • Mass of water = 400 g
  • Molar mass of water = 18.02 g/mol
  • Mole of water = ?

Mole = mass / molar mass

Mole of water = 400 / 18.02

Mole of water = 22.2 moles

<h3>How to de terminethe mole of KBr</h3>
  • Mass of KBr = 0.3 g
  • Molar mass of KBr = 119 g/mol
  • Mole of KBr = ?

Mole = mass / molar mass

Mole of KBr = 0.3 / 119

Mole of KBr = 0.0025 mole

<h3>How to determine the mole fraction of KBr</h3>
  • Mole of KBr = 0.0025 mole
  • Mole of water = 22.2 moles
  • Total mole = 0.0025 + 22.2 = 22.2025 moles
  • Mole fraction of KBr =?

Mole fraction = mole / total mole

Mole fraction of KBr = 0.0025 / 22.2025

Mole fraction of KBr = 0.0001

Learn more about mole fraction:

brainly.com/question/2769009

#SPJ1

6 0
2 years ago
What did Dalton's atomic theory contribute to science?
Serga [27]

Answer:

B

Explanation:

Pasted below is his 5 theory's and all of them are the building blocks of chemistry today.  

1. Matter is made up of atoms that are indivisible and indestructible.

2. All atoms of an element are identical.

3. Atoms of different elements have different weights and different chemical properties.

4. Atoms of different elements combine in simple whole numbers to form compounds.

5. Atoms cannot be created or destroyed. When a compound decomposes, the atoms are recovered unchanged.

4 0
3 years ago
A student is worried about determining if a chemical is radioactive. Which
Mamont248 [21]

Answer:

Hazards Identification

Explanation:

A safety data sheet, SDS, is an informational document provided by the manufacturer or importer of a hazardous chemical detailing the chemical, physical, health, and environmental health hazards associated with the chemical as well as safety precautions in handling the chemical.

Some of the sections in the SDS include:

Product Information: It identifies the chemical as well as its recommended uses. The contact information of the manufacturer is also provided.

Fire fighting methods: It gives measures and guidelines necessary for fighting a fire caused by the chemical.

Physical and chemical properties: states the physical and chemical properties of the chemical substance such as:  appearance, odor, pH, melting/freezing point, boiling point and boiling range, flammability, etc.

Hazards identification: states the hazards of the chemical and the necessary warnings regarding the hazards. Some of the information provided include: hazard classification of the chemical (for example flammable liquid, oxidizing gases,explosives, etc), signal word, hazard statement (for example radioactive), pictograms, precautionary statements, etc.

<em>From the above information provided, the student should refer to the hazards identification section.</em>

8 0
3 years ago
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