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2 years ago

The elements Lithium (Li), Boron (B), and Oxygen (O) are all in the same _________ on the periodic table.

Chemistry

1 answer:

AnnyKZ [126]2 years ago

7 0

Answer:

Period

Explanation:

If we ubicate te period one on the alkaline metals, we can see the lithium, so we go to the borans on te group AIII an we see Boron, move to the rigth on the same sense tou the group AVI we see the Oxygen, we can know that also for the electronic configuration Li:1s²2s¹ B:1s²2s²3p

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The radioactive isotope of lead, Pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.

Marina86 [1]

Answer:

Therefore it will take 7.66 hours for 80% of the lead decay.

Explanation:

The differential equation for decay is

$\frac{dA}{dt}= kA$

$\Rightarrow \frac{dA}{A}=kdt$

Integrating both sides

ln A= kt+c₁

$\Rightarrow A= e^{kt+c_1}$

$\Rightarrow A=Ce^{kt}$ [ $e^{c_1}=C$ ]

The initial condition is A(0)= A₀,

$\therefore A_0=Ce^{0.k}$

$\Rightarrow C=A_0$

$\therefore A=A_0e^{kt}$ .........(1)

Given that the $Pb_{209}$ has half life of 3.3 hours.

For half life $A=\frac12 A_0$ putting this in equation (1)

$\frac12A_0=A_0e^{k\times3.3}$

$\Rightarrow ln(\frac12)= 3.3k$ [taking ln both sides, $ln \ e^a=a$ ]

$\Rightarrow k=\frac{ln \frac12}{3.3}$

⇒k= - 0.21

Now A₀= 1 gram, 80%=0.8

and A= (1-0.8)A₀ = (0.2×1) gram = 0.2 gram

Now putting the value of k,A and A₀in the equation (1)

$\therefore 0.2=1e^{(-0.21)\times t}$

$\Rightarrow e^{-0.21t}=0.2$

$\Rightarrow -0.21t= ln(0. 2)$

$\Rightarrow t= \frac{ln (0.2)}{-0.21}$

⇒ t≈7.66

Therefore it will take 7.66 hours for 80% of the lead decay.

3 0

2 years ago

The type of compound that is most likely to contain a covalent bond is ________.

max2010maxim [7]

The type of substance that is most likely to contain a covalent bond is ONE THAT IS COMPOSED OF ONLY NON METALS.
Covalent bond is a type of chemical bond in which electron pairs are shared among the participating elements in order to achieve the octet form. Covalent bond is usually found among non metals.

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2 years ago

Classify the following as a heterogeneous mixture, homogeneous mixture (solution), or a pure substance: lemonade with no pulp A.

IceJOKER [234]

Answer:

Explanation:

7 0

2 years ago

What did the professer use a catalyst for the flubber experiment

Anettt [7]

In the 1997 movie called, Flubber, the professor used an organic catalyst and a little touch of electricity to make flubber. The organic substance is not known.
Thank you for posting your question here at brainly. I hope the answer helps.

7 0

2 years ago

2. What would be the outcome of a unicellular organism that cannot maintain homeostasis? (1 point)

Juli2301 [7.4K]

Answer:

Option A = it dies

Explanation:

Homeostasis:

It is the ability of organisms to maintain the equilibrium in its internal environment in order to deal with external environmental changes.

If the unicellular organism cannot maintain the homeostasis it would die.

Importance of homeostasis:

It is constant chemical and physical condition of cell. The unicellular organisms in maintained homeostasis condition can grow and reproduce. They respond to the environment and transfer energy. It is the primary objective of unicellular organism other wise they would not survive.

It is very important for them because they totally rely on it and can perform the necessary functions of life.

While in case of multi cellular organisms all cells communicate with each other to maintain the homeostasis.

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3 years ago