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gayaneshka [121]
3 years ago
11

Keeping in mind scientific notation, rounding, and significant figures, what is 25 × 10?

Chemistry
1 answer:
cluponka [151]3 years ago
6 0
It is 300! hope this helps :)
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A chemist wishing to do an experiment requiring 47-Ca2+ (half-life = 4.5 days) needs 5.0 μg of the nuclide. What mass of 47-CaCO
NARA [144]

Answer:

5.8μg

Explanation:

According to the rate or decay law:

N/N₀ = exp(-λt)------------------------------- (1)

Where N = Current quantity,  μg

            N₀ = Original quantity, μg

             λ= Decay constant day⁻¹

              t =  time in days

Since the half life is 4.5 days, we can calculate the  λ from (1) by  substituting N/N₀ = 0.5

0.5 = exp (-4.5λ)

ln 0.5  = -4.5λ

-0.6931 = -4.5λ

λ =   -0.6931 /-4.5

  =0.1540 day⁻¹

Substituting into (1)  we have :

N/N₀ = exp(-0.154t)----------------------------- (2)

To receive 5.0 μg of the nuclide with a delivery time of 24 hours or 1 day:

N = 5.0 μg

N₀ = Unknown

t = 1 day

Substituting into (2) we have

[5/N₀]   = exp (-0.154 x 1)

    5/N₀        = 0.8572

N₀  =  5/0.8572

     =    5.8329μg

    ≈     5.8μg

The Chemist must order 5.8μg  of 47-CaCO3

6 0
3 years ago
According to Newton’s second law of motion, when an object is acted on by an unbalanced force, how will that object respond? It
otez555 [7]

Answer:

C) It will accelerate.  

Explanation:

According to Newton’s second law of motion, when an object is acted on by an unbalanced force, it will accelerate.

An unbalanced force will change the speed or direction (or both) of an object. A change in speed and/or direction is acceleration.

A) is wrong. The object will stop moving only if there is a balanced force in the opposite direction.

B) is wrong. The object will decrease speed only if the unbalanced force has a component opposite to the direction of motion.

d) is wrong. The object will increase speed only if the unbalanced force has a component in the direction of motion.

7 0
3 years ago
Lipids are made up of long hydrocarbon chains, composed of all carbon and hydrogen atoms. this characteristic makes lipids insol
Airida [17]
This is because their tails are hydrophobic and their heads are hydrophilic. Hydrophobic meaning dislikes being near water and hydrophilic meaning likes to be near water. Therefore, they will orientate themselves in such a manner that the heads are facing externally and all the tails are facing together protected by the hydrophilic heads. google a photo of lipid chains in water if you are still confused. I'm not sure if that is what you are asking, but I hope it helps.
8 0
3 years ago
THIS NOT MY WORK. its for my sister. HELP HER
Stolb23 [73]

Answer:

Your answer will be b(molten material from the outer core makes its way to the surface of earth)

Explanation:

5 0
3 years ago
Read 2 more answers
A tank of 0.1m3 volume contains air at 25∘C and 101.33 kPa. The tank is connected to a compressed-air line which supplies air at
Dmitriy789 [7]

Answer:

Amount of Energy = 23,467.9278J

Explanation:

Given

Cv = 5/2R

Cp = 7/2R wjere R = Boltzmann constant = 8.314

The energy balance in the tank is given as

∆U = Q + W

According to the first law of thermodynamics

In the question, it can be observed that the volume of the reactor is unaltered

So, dV = W = 0.

The Internal energy to keep the tank's constant temperature is given as

∆U = Cv((45°C) - (25°C))

∆U = Cv((45 + 273) - (25 + 273))

∆U = Cv(20)

∆U = 5/2 * 8.314 * 20

∆U = 415.7 J/mol

Before calculating the heat loss of the tank, we must first calculate the amount of moles of gas that entered the tank where P1 = 101.33 kPa

The Initial mole is calculated as

(P * V)/(R * T)

Where P = P1 = 101.33kPa = 101330Pa

V = Volume of Tank = 0.1m³

R = 8.314J/molK

T = Initial Temperature = 25 + 273 = 298K

So, n = (101330 * 0.1)/(8.314*298)

n = 4.089891232222

n = 4.089

Then we Calculate the final moles at P2 = 1500kPa = 1500000Pa

V = Volume of Tank = 0.1m³

R = 8.314J/molK

T = Initial Temperature = 25 + 273 = 298K

n = (1500000 * 0.1)/(8.314*298)

n = 60.54314465936812

n = 60.543

So, tue moles that entered the tank is ∆n

∆n = 60.543 - 4.089

∆n = 56.454

Amount of Energy is then calculated as:(∆n)(U)

Q = 415.7 * 56.454

Q = 23,467.9278J

3 0
3 years ago
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