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Lelu [443]
3 years ago
9

What is the half-life of an isotope that decays to 6.25% of its original activity in 18.9 hours?

Chemistry
1 answer:
inessss [21]3 years ago
8 0
Radioactive material obeys 1st order decay kinetics,
For 1st order reaction, we have 
k = \frac{2.303}{t}Xlog \frac{\text{initial conc.}}{\text{final conc.}}
where, k = rate constant of reaction

Given: Initial conc. 100, Final conc. = 6.25, t = 18.9 hours

∴ k = \frac{2.303}{18.9} X log \frac{100}{6.25} = 0.1467 hours^(-1)

Now, for 1st order reactions: half life = \frac{0.693}{k} =  \frac{0.693}{0.1467} = 4.723 hours.


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The hydrogen bonding in water creates ________, a cohesive force that enables one to slightly overfill a glass with water or all
ziro4ka [17]

Answer: -

Surface Tension

Explanation: -

Surface tension is cohesive force created as a result of hydrogen bonding, that enables a liquid drop to have a minimum surface area.

Due to it being cohesive, the water top surface is concave in nature, allowing us to hence slightly overfill a glass with water.

Due to surface tension, the surface of water behaves like a stretched membrane, allowing dense objects like a length wise steel needle to float on water.

Thus, the hydrogen bonding in water creates __surface tension__, a cohesive force that enables one to slightly overfill a glass with water or allows denser objects, such as a lengthwise steel needle, to float on water

8 0
4 years ago
How many oxygen atoms are in 4.00g of quartz?
Rufina [12.5K]

Answer:

Rounding for significant figures gives us a final answer of 3.41×1022 atoms 3.41 × 10 22 a t o m s atoms of oxygen.

4 0
2 years ago
A spherical balloon initially contains 25m3 of helium gas at 20o C and 150 kPa. A valve is now opened and the helium is allowed
Tpy6a [65]

Find the attachment for complete solution

6 0
3 years ago
The following question appears on a quiz: ""You fill a tank with gas at 60°C to 100 kPa and seal it. You decrease the temperatu
dusya [7]

Answer: The final pressure will decrease ad the value is 85 kPa

Explanation:

To calculate the final pressure of the system, we use the equation given by Gay-Lussac Law. This law states that pressure of the gas is directly proportional to the temperature of the gas at constant pressure.

Mathematically,

\frac{P_1}{T_1}=\frac{P_2}{T_2}

where,

P_1\text{ and }T_1 are the initial pressure and temperature of the gas.

P_2\text{ and }T_2 are the final pressure and temperature of the gas.

We are given:

P_1=100kPa\\T_1=60^0C=(60+273)K=333K\\P_2=?\\T_2=10^0C=(10+273)K=283K

Putting values in above equation, we get:

\frac{100kPa}{333K}=\frac{P_2}{283K}\\\\P_2=85kPa

Hence, the final pressure will decrease ad the value is 85 kPa

8 0
3 years ago
Covalent bonds usually occur between atoms that have
marta [7]

Answer: A: high ionization energies; high electron affinitlies.

Explanation: Covalent bonds are basically about sharing of electrons between two atoms to achieve that stable structure. They are formed between two atoms when both have similar tendencies to attract electrons to themselves (i.e., when both atoms have identical or fairly similar ionization energies and electron affinities). Covalent bonding usually occurs between two non-metals.

For effective and proper bonding, the two atoms involved in the covalent bonding exercise should be small and hungry for electrons. This is to enable the nuclei of both atoms to effectively attract and hold the shared electron(s) in place; hence, the need for high ionization energies & high electron affinities for a more effective covalent bonding.

7 0
3 years ago
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