2moles
1.20moles
0.5mole
Explanation:
Given parameters:
Mass of He = 8g
Mass of Zn = 78g 
Volume of oxygen gas= 11.2L
Unknown:
Number of moles of He, Zn = ?
Number of moles of oxygen gas = ?
Solution;
Number of moles of substances is given as :
Number of moles = 
molar mass of He = 4g/mol
molar mass of Zn = 65.4g/mol
Number of moles of He = 
= 2moles
Number of moles of Zn = 
1.20moles
For gases at STP;
Number of moles = 
Number of moles = 
= 0.5mole
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023x10^23 He atoms. 1 mole Of Helium = Weight of Helium/4Weight of Helium = 1*4 = 4 grams 1 mole of Helium contains 6.023*10²³ (Avogadro number) atoms. MULTIPLY BY 98.2g FOR COMPLETE ANSWER
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The following chemical equation 2C8H18(g)+ 25O2(g)→ 16CO2(g)+ 18H2O(g) is balance and 48.64 grams of oxygen is required in the combustion of octane in gasoline.
<h3>What is combustion?</h3>
When burning of petrol happens and releases toxic hydrocarbons and carbon dioxide gasses with some amount of oxygen is known as combustion.
The balanced chemical equation is 2C8H18(g)+ 25O2(g)→ 16CO2(g)+ 18H2O(g),
number of moles = mass / molar mass
substituting the value in equation,
number of moles = 14 / 114g = 0.122 moles.
number of moles of oxygen 0.122 × 0.122 moles. = 1.52 moles.
1.52 = mass / 32
mass = 48.64 gram.
Therefore,48.64 grams of oxygen is required in the combustion of octane in gasoline.
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<h3>
Answer: Choice B</h3>
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Explanation:
The big X represents some placeholder for another letter (or pair of letters) found in the periodic table of elements. For instance, the X might represent hydrogen (H) or helium (He).
The numbers off to the side refer to the number of protons and neutrons.
The larger number up top is the protons + neutron count.
The smaller number is the number of protons only.
For example, writing 
means there are 6 protons + 8 neutrons = 14 total.
The proton number is the key indicator of what element we're dealing with. If we want the elements to be the same, they need to have the same bottom number. Choices A, C, and D are ruled out because of this.
<u>Choice B is the answer</u> because the 6 at the bottom tells us we're dealing with carbon with 6 protons. Carbon-12 has 6 protons + 6 neutrons to get 6+6 = 12 items total. So the naming of "carbon-12" helps us figure out which isotope of carbon we're dealing with. The abundance of carbon-12 is somewhere around 98.84% and 99.04%
In slight contrast, carbon-13 has 1 extra neutron compared to carbon-12 (6 protons + 7 neutrons = 13 total). The abundance of carbon 13 is roughly between 0.96% and 1.16%.
Even more rare is carbon-14. The percentage value is so very very small that it's practically 0% (though this isotope is around in small trace forms).
Side note: carbon-11 is also an isotope of carbon, but it's not found in nature. Rather, it's manmade or synthetic.
