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stellarik [79]
2 years ago
12

A particular radioactive isotope has a half-life of (2.50+a) hours. if you have (24.5+b) g of the isotope at 10:00 am, how much

will you have at 7:30pm? give your answer in grams (g)and with 3 significant figures.
Chemistry
1 answer:
gavmur [86]2 years ago
3 0
Its a not b and i dont know the reast

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Convert 1.21 kg to grams
MissTica

Answer:

1210 grams

Explanation:

Message me for extra info.

snap- parkguy786

7 0
2 years ago
Read 2 more answers
Small beads of iridium-192 are sealed in a plastic tube and inserted through a needle into breast tumors. If an Ir-192 sample ha
Stells [14]

Answer:

296.1 day.

Explanation:

  • The decay of radioactive elements obeys first-order kinetics.
  • For a first-order reaction: k = ln2/(t1/2) = 0.693/(t1/2).

Where, k is the rate constant of the reaction.

t1/2 is the half-life time of the reaction (t1/2 = 1620 years).

∴ k = ln2/(t1/2) = 0.693/(74.0 days) = 9.365 x 10⁻³ day⁻¹.

  • For first-order reaction: <em>kt = lna/(a-x).</em>

where, k is the rate constant of the reaction (k = 9.365 x 10⁻³ day⁻¹).

t is the time of the reaction (t = ??? day).

a is the initial concentration of Ir-192 (a = 560.0 dpm).

(a-x) is the remaining concentration of Ir-192 (a -x = 35.0 dpm).

<em>∴ kt = lna/(a-x)</em>

(9.365 x 10⁻³ day⁻¹)(t) = ln(560.0 dpm)/(35.0 dpm).

(9.365 x 10⁻³ day⁻¹)(t) = 2.773.

<em>∴ t </em>= (2.773)/(9.365 x 10⁻³ day⁻¹) =<em> 296.1 day.</em>

5 0
2 years ago
Which of the following statements concerning hydrocarbons is/are correct?
Alona [7]

Answer:

1.  Saturated hydrocarbons may be cyclic or acyclic molecules.

2.  An unsaturated hydrocarbon molecule contains at least one double bond.

Explanation:

Hello,

In this case, hydrocarbons are defined as the simplest organic compounds containing both carbon and hydrogen only, for that reason we can immediately discard the third statement as ethylenediamine is classified as an amine (organic chain containing NH groups).

Next, as saturated hydrocarbons only show single carbon-to-carbon bonds and carbon-to-hydrogen bonds, they may be cyclic (ring-like-shaped) or acyclic (not forming rings), so first statement is true

Finally, since we can find saturated hydrocarbons which have single carbon-to-carbon and carbon-to-hydrogen bonds only and unsaturated hydrocarbons which could have double or triple bonds between carbons and carbon-to-hydrogen bonds, the presence of at least one double bond makes the hydrocarbon unsaturated.

Therefore, first and second statements are correct.

Best regards.

6 0
2 years ago
In what situation do we use a volumetric flask, conical flask, pipette and graduated cylinder? Explain your answer from accuracy
Ad libitum [116K]
A volumetric flask is used to contain a predetermined volume of substance and only measures that volume, for example 250 ml.
Conical flasks can be used to measure the volume of substances but the accuracy they provide is usually up to 10ml. Conical flasks are used in titrations, reactions where the liquid may boil, and reactions which involve stirring. 
Pippettes are of two types, volumetric and graduated. Pippettes are used where high accuracy is required and volumetric pippettes come in as little as 1 ml. Pippettes are usually used in titrations.
Graduated cylinders come in a wide variety of sizes and their accuracy can be down to as much as 1 ml. They are used to contain liquids.
3 0
2 years ago
A poundal is the force required to accelerate a mass of 1 lbm at a rate of 1 ft/s2, and a slug is the mass of an object that wil
Darya [45]
Remember the formula as per the second Law of Newton: F = m*a

And also remember that the weight is the force with which the mass is attracted by the planet (or satellite in the case of the moon).

With that information you can answer the questions:

a) Weight = F = m*a

m = 175 slugs = 175 lbm

i) Earth

a = 32.17 ft/s^2

Weight on Earth = 175 lbm * 32.17 ft / s^2 = 5,629.75 poundal

ii) Moon

a = [1/6] 32.17 ft/s^2

Weight on the Moon = [1/6]*5,629.75 poundal = 938.29 poundal

b) Force = 355 poundal
m = 25.0 slug

a in m/s^2 = ?

First calculate the force in ft/s^2

F = m*a => a = F/m = 355 poundal / 25.0 slug = 14.2 ft/s^2

Conversion:

14.2 ft / s^2 * [ 0.3048 m/ft] = 4.32816 m/s^2

Answer: 4.33 m/s^2


8 0
2 years ago
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