1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Tomtit [17]
3 years ago
11

Strontium 90 (sr-90, a radioactive isotope of strontium, is present in the fallout resulting from nuclear explosions. it is espe

cially hazardous to animal life, including humans, because, upon ingestion of contaminated food, it is absorbed into the bone structure. its half-life is 27 years. if the amount of sr-90 in a certain area is found to be four times the "safe" level, find how much time must elapse before the safe level is reached.
Chemistry
1 answer:
Artyom0805 [142]3 years ago
7 0
This is a relatively easy half-life problem.
Whenever a half-life has expired, one half of the radioactive isotope will no longer be present.
When 2 half-lives have occurred, then one quarter of the isotope remains.
Therefore, the strontium - 90 will be at a safe level in 54 years.
 

You might be interested in
Write the net cell equation for this electrochemical cell. Phases are optional. Do not include the concentrations. Co ( s ) ∣ ∣
Tatiana [17]

Answer: The overall equation will be Co(s)+2Ag^+(aq)\rightarrow Co^{2+}(aq)+Ag(s)

Explanation:

The representation is given by writing the anode on left hand side followed by its ion with its molar concentration. It is followed by a salt bridge. Then the cathodic ion with its molar concentration is written and then the cathode.

Oxidation reaction is defined as the reaction in which a substance looses its electrons. The oxidation state of the substance increases.

Anode : Co(s)\rightarrow Co^{2+}(aq)+2e^{-}

Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced.

Cathode : Ag^+(aq)+e^{-1}\rightarrow Ag(s)  \times 2

The number of electrons lost must be equal to the number of electrons gained , thus overall equation will be :

Co(s)+2Ag^+(aq)\rightarrow Co^{2+}(aq)+Ag(s)

5 0
3 years ago
What do you mean by chemical reaction ?​
kherson [118]

A chemical reaction is a reaction that changes the molecular structure and is normally irreversible.

6 0
3 years ago
In a chemical reaction 300 grams of reactant A combined with 100 grams of reactant B both A and B react to completion what is th
ivann1987 [24]

Answer: 1.2

Explanation:

3 0
3 years ago
( pls help me) brainlest answer too
bonufazy [111]
<span>
4.) Heat is transferred through a piece of metal by _____.
conduction

Conduction happens when both items are in close contact. In a piece of metal. In this case, the heat transfers gradually into the other ends of the object. This makes the transfer rate is slow on a long object with a low surface area.


5.) Heat from the sun travels to earth by _____.
radiation

</span>Sun energy comes from a reaction that will produce a light and heat and it is transferred to the earth by radiation. While conduction and convection need contact with the object, radiation doesn't.  Radiation can travels a very long distance, that is why the heat could be delivered to the earth.
<span>

6.) Energy in a vacuum travels by ___.
radiation

</span>One of the examples for energy travels in a vacuum would be sunlight. Sun and earth are separated by vacuum space which means there is no direct contact between earth and sun. That means conduction and convection are not possible.
<span>

7.) In a convection current _____.
</span><span>C.)cool fluid is more dense, and therefore, sinks
</span><span>
Cool fluid have lower volume, thus become denser than warm fluid. Since its density higher than the warm fluid, it will sinks and moves toward the earth. The warm fluid also rises to replace the cool fluid.


8.) Nuclear reactions occurring in the Sun _____. Select all that apply.
generate light
generate heat
fuse atoms of hydrogen to make helium atoms

Sun is bright and hot, which means it produces light and heat. The reaction should be producing energy, not absorbing energy. The reaction that produces that energy would be the fusion reaction of hydrogen into helium.


9.) Which of the following statements is true?
</span><span>C.)The sun's energy comes from the nuclear reactions of changing hydrogen into helium.
</span><span>The sun reaction is right, it is forming helium using hydrogens.
Transfer of heat in liquid mostly happens because convection which need direct contact. But the heat can transfer by radiation too, so its a bit ambiguous.
Temperature represents the average kinetic energy of the molecule and it is different with heat/thermal energy.</span>
3 0
3 years ago
Read 2 more answers
PLEASE HELP 30 POINTS WILL GIVE BRAINLIEST
nikitadnepr [17]

Tachyon is not a particle.

7 0
4 years ago
Read 2 more answers
Other questions:
  • Nitrogen fixing bacteria in soil turns nitrogen gas into
    10·1 answer
  • Which of the following statements regarding energy changes during a reaction are true?. 1) If the heat of reaction, ΔH, is negat
    11·2 answers
  • Which compounds yield hydrogen ions as the only positive ions in an aqueous solution?
    13·2 answers
  • HELPPPPP
    13·1 answer
  • Assuming that light is composed of particles (photons), how do you think you can adjust the conditions in the simulation to make
    14·1 answer
  • Din ce este alcatuita o molecula de amoniac?
    14·1 answer
  • 5.22*10^-3 = ?*10^-2
    10·1 answer
  • The new element "Leo (L)" has three stable isotopes: L-82 (exact mass: 81.8735), L-85 (exact mass: 84.8322), and L-86
    12·1 answer
  • Dry ice changes from a solid directly into a gas at room temperature. Sublimation is the transition of a substance directly from
    13·1 answer
  • I need help ASAP ... please
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!