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11111nata11111 [884]
4 years ago
10

How many Helium atoms are in 12 grams of Helium?

Chemistry
1 answer:
horsena [70]4 years ago
6 0
12gHe/1 × 1molHe/4.0026g × 6.02x10^23atomHe/1mol = 1.8 atoms
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Boron has two naturally-ocurring isotopes. Boron-10 has an abundance of 19.8% and actual mass of 10.013 amu, and boron-11 has an
aniked [119]

Answer:

Average atomic mass = 10.812 amu

Explanation:

The formula for the calculation of the average atomic mass is:

Average\ atomic\ mass=(\frac {\%\ of\ the\ first\ isotope}{100}\times {Mass\ of\ the\ first\ isotope})+(\frac {\%\ of\ the\ second\ isotope}{100}\times {Mass\ of\ the\ second\ isotope})

Given that:

<u>For first isotope, Boron-10: </u>

% = 19.8 %

Mass = 10.013 amu

<u>For second isotope, Boron-11: </u>

% = 80.2 %

Mass = 11.009 amu

Thus,  

Average\ atomic\ mass=\frac{19.8}{100}\times {10.013}+\frac{80.2}{100}\times {11.009}=1.982574+8.829218=10.811792

<u>Average atomic mass = 10.812 amu</u>

6 0
3 years ago
Read 2 more answers
Why are changes of state, for example, liquid water changing to steam, not considered to be chemical changes?
GREYUIT [131]

Answer:

A liquid changing to a gas is considered a physical change because it involves a change in one or more physical properties, but no change in the fundamental components that make up the substance.

5 0
3 years ago
How many places are there for electrons in the third shell of an atom?
Dafna1 [17]
Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.
7 0
3 years ago
For the reaction, identify the Lewis acid and the Lewis base.<br> AlF3 + CH3F → CH3+ + [AlF4]-
Ivanshal [37]
Answer:
            AlF₃ is Lewis Acid

            CH₃F is Lewis Base

Explanation:
                     According to Lewis concept ,"those compounds which donate pair of electrons are called as Lewis Base and those accepting pair of electrons are called as Lewis Acid.

In Given Reaction,
<span>                               AlF</span>₃<span> + CH</span>₃<span>F → CH</span>₃⁺<span> + [AlF</span>₄<span>]</span>⁻

AlF₃ is acting as acid because the octet of Al is not complete, hence it has tendency to accept electrons.

CH₃F is acting as a base because the F atom containing three lone pair of electrons can donate it to Al metal resulting in the formation of electrophile i.e. CH₃⁺.
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3 years ago
A type of potential energy that is associated with objects that can be stretched or compressed is called ??
Scorpion4ik [409]
The answer is C. Elastic potential energy
4 0
3 years ago
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