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3 years ago

5

The Periodic Table is arranged according to?

2 answers:

Serhud [2]3 years ago

7 0

Answer:

The number of protons each element has.

Explanation:

The periodic table is arranged by atomic number, which is the number of protons in the nucleus of each element.

lesya692 [45]3 years ago

5 0

Answer:

The number of protons each element has.

Explanation:

<u>The number of protons each element has is also known as the atomic number.</u> Elements are arranged from left to right and top to bottom in order of increasing atomic number. The order generally coincides with increasing atomic mass. The rows are called periods.

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PolarNik [594]

Answer:

Answer D. Picture II shows a chemical change, because the same substance changes form

Explanation:

This is the temperature that water molecules slow down enough to stick to each other and form a solid crystal

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2 years ago

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In the reaction n2 + 3h2 ---> 2nh3, how many grams of nh3 are produced if 25.0 g n2 reacts with excess h2? question 10 option

Lisa [10]

Molar mass of N2 = 28

Moles of N2 = 25 / 28 = 0.89

So, moles of NH3 produce = 2 x 0.89 = 1.78

Note: H2 is in excess. so no need to care about it.

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3 years ago

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.

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3 years ago

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nasty-shy [4]

You're answer is 250 apples for 25 pies

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Blizzard [7]

Answer:

Explanation:

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3 years ago

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