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3 years ago

Which statements best describe fossils? Check all that apply.

Chemistry

2 answers:

nikdorinn [45]3 years ago

3 0

Answer:

2&3&5

Explanation:

fossils are and can be all of the above

ololo11 [35]3 years ago

3 0

Answer:

2,3,5

Explanation:

i got it right

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When 1.00 g of boron is burned in o2(g) to form b2o3(s), enough heat is generated to raise the temperature of 733 g of water fro

Bas_tet [7]

Answer: For this problem, you would need to know the specific heat of water, that is, the amount of energy required to raise the temperature of 1 g of water by 1 degree C. The formula is q = c X m X delta T, where q is the specific heat of water, m is the mass and delta T is the change in temperature. If we look up the specific heat of water, we find it is 4.184 J/(g X degree C). The temperature of the water went up 20 degrees. 4.184 x 713 x 20.0 = 59700 J to 3 significant digits, or 59.7 kJ. Now, that is the energy to form B2O3 from 1 gram of boron. If we want kJ/mole, we need to do a little more work. To find the number of moles of Boron contained in 1 gram, we need to know the gram atomic mass of Boron, which is 10.811. Dividing 1 gram of boron by 10.811 gives us .0925 moles of boron. Since it takes 2 moles of boron to make 1 mole B2O3, we would divide the number of moles of boron by two to get the number of moles of B2O3. .0925/2 = .0462 moles...so you would divide the energy in KJ by the number of moles to get KJ/mole. 59.7/.0462 = 1290 KJ/mole.

7 0

3 years ago

Which statements accurately describe volume? Check all that apply.

lesantik [10]

Where is the chooses for you question

8 0

3 years ago

IF 3.25 mol of argon gas occupies a volume of 100. L at a particular temperature and

Serga [27]

Answer:

435.38 L

Explanation:

From the question given above, the following data were obtained:

Initial mole (n₁) = 3.25 mole

Initial volume (V₁) = 100 L

Final mole (n₂) = 14.15 mole

Final volume (V₂) =?

The final volume occupied by the gas can be obtained as follow:

V₁/n₁ = V₂/n₂

100 / 3.25 = V₂ / 14.15

Cross multiply

3.25 × V₂ = 100 × 14.15

3.25 × V₂ = 1415

Divide both side by 3.25

V₂ = 1415 / 3.25

V₂ = 435.38 L

Thus, the final volume of the gas is 435.38 L

3 0

3 years ago

PLEASE ANSWER Which is/are true?

Alona [7]

You have to check each statement, so this is equivalent to 5 different questions.

Answers:

The true statements are:

b. Si has valence electrons in the n = 3 energy level.

d. Xe has valence electrons in the n = 5 energy level.

Explanations:

a. Li has valence electrons in the n = 1 energy level.

Answer: False.

Valence electrons are the electrons in the outermost main energy level (shell of electrons).

To determine where the valence electrons are, you build the electron configuration, using Aufbau rules to predict the orbital filling: in increasing order of energy.

The atomic number of lithium (Li) is 3. Hence, you have to distribute 3 electrons, and so its electron confiuration is:

1s² 2s¹

The only valence electron is in the 2s orbital, i.e. in the n = 2 energy level.

b. Si has valence electrons in the n = 3 energy level.

Answer: True

Silicon (Si) has atomic number 14, so you have to distribute 14 electrons in increasing order of energy:

1s² 2s² 2p⁶ 3s² 3p²

Thus, Si has five valence electrons, and they are in the n = 3 energy level.

c. Ga has valence electrons in the n = 3 energy level.

Answer: False

Gallium has atomic number 31, so you have to distribute 31 electrons, filling the orbitals in increasing order of enery.

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p¹

The highest energy level is 4. This is where the valence electrons are. So, Ga has the valence electrons in the n = 4 level (not n = 3 as the statement describes).

d. Xe has valence electrons in the n = 5 energy level.

Answer: True

The atomic number of Xe is 54.

Using the short notation (noble gas notation), and filling the orbitals in increasing order of energy, you get the configuration:

[Kr] 5s² 4d¹⁰ 5p⁶.

Hence, the valence electrons are in the n ) 5 level, such as the statement describes.

e. P has valence electrons in the n = 2 energy level.

Answer: False

Phosphorus (P) has atomic number 15, hence there are 15 electrons.

The electron configuration following the increasing order of energy, which you can remember using Aufbau rules, is:

1s² 2s² 3s² 3p³

Then, the valence electrons are in the n = 3 energy level; not in the n = 2 energy level.

3 0

3 years ago

How will you prepare 10mL of 0.050M HCl from a 0.10M solution of HCl

vichka [17]

M₁V₁ = M₂V₂

(0.050M)*(10 mL) = (0.10M)*(x)

x = 5 mL

You would take 5 mL of the 0.10 M solution of HCl and add 5 mL of deionized water. Therefore, the total volume will be 10 mL and it will have a molarity of 0.050.

7 0

3 years ago