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kumpel [21]
3 years ago
8

A student submits the following work on the mass number, but he has made a few mistakes. Select the sentences that are incorrect

.
Calculating the mass number for an atom requires that we know the atomic number and the number of protons in the atom’s nucleus. The mass number then gives us the average weight of atoms of a given element. Specifically, these units are calibrated by setting the mass number for carbon-12 as 12 atomic mass units. Neutrons and protons have the same masses. However, as long as the number of protons equals the number of neutrons, the values balance out and we always obtain a whole number for the mass number.
Chemistry
1 answer:
rewona [7]3 years ago
7 0

Answer

 

Calculating the mass number for an atom requires that we know the atomic number and the number of protons in the atom’s nucleus. The mass number then gives us the average weight of atoms of a given element. However, as long as the number of protons equals the number of neutrons, the values balance out and we always obtain a whole number for the mass number.

Explanation:

those 3

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A chemist dissolves 239 mg of pure potassium hydroxide in enough water to make up of solution. Calculate the pH of the solution.
PSYCHO15rus [73]

Answer: the pH is 11.78

Explanation:Please see attachment for explanation

7 0
3 years ago
The standard entropy change of a reaction has a positive value. This reaction results in: Select the correct answer below: a dec
Ira Lisetskai [31]

Explanation:

The standard entropy change of a reaction has a positive value. This reaction results in an increase in entropy.

Positive entropy means the system has increased its degree of disorderness.

5 0
3 years ago
Atoms have been traditionally viewed as being composed of three different types of particles: protons, neutrons, and electrons.
sattari [20]

Answer:

See explanation

Explanation:

Before the advent of the wave-particle duality theory proposed by Louis de Broglie, there was a sharp distinction between mater and waves.

However, Louis de Broglie introduced the idea that mater could display wave-like properties.  Erwin Schrödinger developed this idea into what is now known as the wave mechanical model of the atom.

In this model, electrons are regarded as waves. We can only determine the probability of finding the electron within certain high probability regions within the atom called orbitals.

This idea has been the longest surviving atomic model and has greatly increased our understanding of atoms.

7 0
3 years ago
FIRST GETS BRAINLIEST
lisov135 [29]

Answer:

0.07172 L = 7.172 mL.

Explanation:

  • We can use the general law of ideal gas: <em>PV = nRT. </em>

where, P is the pressure of the gas in atm (P = 1.0 atm, Standard P).

V is the volume of the gas in L (V = ??? L).

n is the no. of moles of the gas in mol (n = 3.2 x 10⁻³ mol).

R is the general gas constant (R = 0.0821 L.atm/mol.K),

T is the temperature of the gas in K (T = 273 K, Standard T).

<em>∴ V = nRT/P =</em> (3.2 x 10⁻³ mol)(0.0821 L.atm/mol.K)(273 K)/(1.0 atm) = <em>0.07172 L = 7.172 mL.</em>

8 0
3 years ago
Some radioactive nuclides have very short half-lives, for example, I-31 has a half-life of approximately 8 days. Pu-234, by comp
lorasvet [3.4K]

Answer:

Here's what I find.

Explanation:

Iodine-131

Iodine-131 is both a beta emitter and a gamma emitter.

_{53}^{131}\text{I}\longrightarrow \, _{54}^{131}\text{Xe} +\, _{-1}^{0}\text{e} +\, _{0}^{0}\gamma

About 90 % of the energy is β-radiation and 10 % is γ-radiation. Both forms are highly energetic.

The main danger is from ingestion. The iodine concentrates in thyroid gland, where the β-radiation destroys cells up to 2 mm from the tissues that absorbed it.

Both the β- and γ-radiation cause cell mutations that can later become cancerous. Small doses, such as those absorbed from the nuclear disasters in the Ukraine and Japan, can cause cancers years after the original iodine has disappeared.

Plutonium-239

Plutonium-239 is an alpha emitter.

_{94}^{239}\text{U} \longrightarrow \, _{92}^{235}\text{Xe} + \, _{2}^{4}\text{He}

Alpha particles cannot penetrate the skin, so external exposure isn't much of a health risk.

However, they are extremely dangerous when they are inhaled and get inside cells. They travel first to the blood or lymph system and later to the bone marrow and liver, where they cause up to 1000 times more chromosomal damage than beta or gamma rays.

It takes about 20 years for plutonium to be eliminated from the liver around 50 years for from the skeleton, so it has a long time to cause damage.

6 0
3 years ago
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