Considering the definition of STP conditions, 3.35 moles of helium are contained within the balloon.
<h3>Definition of STP condition</h3>
The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C are used and are reference values for gases. And in these conditions 1 mole of any gas occupies an approximate volume of 22.4 liters.
<h3>Amount of moles of helium within the balloon</h3>
In this case, you know that scientist fills a large, tightly sealed balloon with 75,000 mL of helium at STP.
So, you can apply the following rule of three: if by definition of STP conditions 22.4 liters are occupied by 1 mole of helium, 75 L (75 L= 75000 mL, being 1 L= 1000 L) are occupied by how many moles of helium?
<u><em>amount of moles of helium= 3.35 moles</em></u>
Finally, 3.35 moles of helium are contained within the balloon.
Learn more about STP conditions:
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Ca ionises into Ca^2+. Ca^2+ will be attracted to O^2- ions in the water, since opposite charges attract. (Hydrogen in water forms H^+)
Answer:
0.6 moles of CaO will produced.
Explanation:
Given data:
Mass of calcium = 23.9 g
Moles of CaO produced = ?
Solution:
Chemical equation:
2Ca + O₂ → 2CaO
Number of moles of calcium:
Number of moles = mass/ molar mass
Number of moles = 23.9 g / 40 g/mol
Number of moles = 0.6 mol
Now we will compare the moles of calcium and CaO.
Ca : CaO
2 : 2
0.6 : 0.6
0.6 moles of CaO will produced.
The atomic number (Z) of the 3 elements F, Ne, and Na, are 9, 10, and 11.
Explanation:
Now Z refers to the number of protons in the element's nucleus, and protons are POSITIVELY charged particles. So a fluoride ion, F−, has 10 electrons rather than 9 (why?), a neutral neon atom has 10 electrons, and a sodium ion, Na+, also has 10 electrons (why?).
So the 3 species are ISOELECTRONIC; they possess the same number of electrons.
You should look at the Periodic Table to confirm the electron number. Elements are (usually) electrically neutral (sometimes they can be ionic if they have lost or gained electrons). If there are 10 positively charged protons in the nucleus, there are NECESSARILY 10 electrons associated with the NEUTRAL atom. I don't know WHY I am capitalizing certain WORDS.
You might ask why sodium will form a positive ion, Na+, whereas F forms a negative ion, F−. This again is a Periodic phenomenon, and explicable on the basis of the electronic structure that the Table formalizes.
Neutral metals tend to be electron-rich species, which have 1 or more electrons in a valence shell remote from the nuclear charge. On the other hand, neutral non-metals have valence electrons in incomplete shells, that do not effectively shield the nuclear charge. The demonstrable consequence is that metals lose electrons to form positive ions, whereas non-metals gain electrons to form negative ions.
Answer:
The only true statement is:
- a. <u><em>Alpha particles have a mass number of 4</em></u>
Explanation:
<em>Alpha particles</em> are radiactive particles equivalent to a helium nucleus, so they have two protons and two neutrons.
Hence, alpha particles, α, are represented as:
The superscript 4 to the left of the chemical symbol is the <em>mass number:</em> 2 protons + 2 neutrons = 4
The subscript 2 to the left of the chemical symbol is the atomic number: 2 protons = 2.
Hence, the statement "a. Alpha particles have a mass number of 4" is true.
As for the other statements, you have:
<em>b. Alpha particles have a nulear charge of +1:</em> <u>false</u>
Since, these particles are the nucleous of the helium atom, the nuclear charge equals the number of protons of this atom: +2. Hence, the statement is false.
c. <em>Alpha particle formation is accompanied by the conversion of a proton into a neutron</em> and d. <em>Alpha particle formation is accompanied by the conversion of a neutron into a proton</em>. <u>(both false</u>)
The conversion of a protons into a neutrons and the conversion of a neutron into a proton are product of other kind of radiactive desintegrations.
- The conversion of a proton into a neutron involves the emission of a positron ( particle with same mass as the electron but positive charge) from the nucleus, which is represented as ⁰₊₁β.
- The conversion of a neutron into a proton involves the emssion of an electron from the nucleus, which is the emission of a beta particle represented as ⁰₋₁β.
Therefore, these last two statements are also false.
