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3 years ago

5

A star is mainly made of hydrogen gas, but most classes of stars include other elements such as helium, calcium, and other heavi

er elements and molecules.
Group of answer choices

True

False

2 answers:

Xelga [282]3 years ago

6 0

That would be true, since most other stats include helium, calcium, etc

Sidana [21]3 years ago

4 0

The answer is true! :)

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8. The following system contains 20.0 psi each of gases A and B in the end bulbs with an evacuated bulb in the centre. Both stop

Effectus [21]

Answer:

13.3

Explanation:

Before opening the stopcocks you have 40psi in total.

After that, those 40psi will be divided into 3bulbs, so 40/3=13.3psi for the system.

3 0

3 years ago

Water has a boiling point of 100.0°C and a Kb of 0.512°C/m. What is the boiling

Reil [10]

Answer:

The boiling point of a 8.5 m solution of Mg3(PO4)2 in water is<u> 394.91 K.</u>

Explanation:

The formula for molal boiling Point elevation is :

$\Delta T_{b} = iK_{b}m$

$\Delta T_{b}$ = elevation in boiling Point

$K_{b}$ = Boiling point constant( ebullioscopic constant)

m = molality of the solution

<em>i =</em> Van't Hoff Factor

Van't Hoff Factor = It takes into accounts,The abnormal values of Temperature change due to association and dissociation .

In solution Mg3(PO4)2 dissociates as follow :

$Mg_{3}(PO_{4})_{2}\rightarrow 3Mg^{2+} + 2 PO_{4}^{3-}$

Total ions after dissociation in solution :

= 3 ions of Mg + 2 ions of phosphate

Total ions = 5

<em>i =</em> Van't Hoff Factor = 5

m = 8.5 m

$K_{b}$ = 0.512 °C/m

Insert the values and calculate temperature change:

$\Delta T_{b} = iK_{b}m$

$\Delta T_{b} = 5\times 0.512\times 8.5$

$\Delta T_{b} = 21.76 K$

Boiling point of pure water = 100°C = 273.15 +100 = 373.15 K

$\Delta T_{b} = T_{b} - T_{b}_{pure}$

$T_{b}_{pure}$ = 373.15 K[/tex]

21.76 = T - 373.15

T = 373.15 + 21.76

T =394.91 K

8 0

3 years ago

How would having too much sample in the melting point tube most likely affect the melting point measurement? Select the correct

oksano4ka [1.4K]

Answer:

2-4 mm height of capillary tube.

Explanation:

Sample should be around 2-4 mm in height.

It should be packed well so that it does not have air packets that caues the lowering of melting point.

If you take greater amount, then there will be needed more heat, resulting a wide range of melting point.

7 0

3 years ago

Where do the nitrogen bases that are floating go

Vesna [10]

they pair up with other bases to make up the rungs of the DNA ladder

8 0

4 years ago

What is the total number of valence electrons in the dot structure of CBr4? Explain how you determined this answer. What is the

Mnenie [13.5K]

Answer:- There are 32 valence electrons and it's tetrahedral in shape.

Explanations:- Atomic number of carbon is 6 and it's electron configuration is $1s^22s^22p^2$ . It has 4 electrons in the outer most shell means it has 4 valence electrons.

Atomic number of Br is 35 and it's electron configuration is $1s^22s^22p^63s^23p^64s^23d^1^04p^5$ . It has 7 electrons in the outer most shell(2 in 4s and 5 in 4p) .

There is one C and four Br in the given compound. So, total number of valence electrons = 4+4(7) = 4+28 = 32

Four Br atoms are bonded to the central carbon atom and also there isn't any lone pair present on carbon. It makes it tetrahedral.

5 0

3 years ago