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Serga [27]
3 years ago
8

What are atoms made of

Chemistry
2 answers:
Olegator [25]3 years ago
7 0
Protons, neutrons, and electrons.
amid [387]3 years ago
3 0
Atoms are made of particles called protons and neutrons.
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How many kJ of heat are released by the reaction of 25.0 g of Na2O2(s) in the following reaction? (M = 78.0 g/mol for Na2O2)
solong [7]

-20.16 KJ of heat are released by the reaction of 25.0 g of Na2O2.

Explanation:

Given:

mass of Na2O2 = 25 grams

atomic mass of Na2O2 = 78 gram/mole

number of mole = \frac{mass}{atomic mass of 1 mole}

                          = \frac{25}{78}

                          =0. 32 moles

The balanced equation for the reaction:

2 Na2O2(s) + 2 H2O(l) → 4 NaOH(aq) + O2(g) ∆Hο = −126 kJ

It can be seen that 126 KJ of energy is released when 2 moles of Na2O2 undergoes reaction.

similarly 0.3 moles of Na2O2 on reaction would give:

\frac{126}{2} = \frac{x}{0.32}

x = \frac{126 x 0.32}{2}

 = -20.16 KJ

Thus, - 20.16 KJ of energy will be released.

6 0
3 years ago
Scientists Discuss time and how old the Earth is. How do they measure the idea
Firdavs [7]

The following is the introduction to a special e-publication called Determining the Age of the Earth (click the link to see a table of contents). Published earlier this year, the collection draws articles from the archives of Scientific American. In the collection, this introduction appears with the title, “Stumbling Toward an Understanding of Geologic Timescales.”

4 0
2 years ago
Whetes the most of the mass of our solar system today
Simora [160]
Planets, black wholes gravity
3 0
2 years ago
How many moles are in 5.0 x 10^25 atoms of iron?
Andreas93 [3]

Hello!

To find the number of moles that are in the given amount, we need to divide the total number of atoms by Avogadro's number, which is 1 mole is equal to 6.02 x 10^23 atoms.

5.0 x 10^25 / 6.02 x 10^23 ≈ 83.0564

Therefore, there are about 83.06 moles of iron (sigfig: 83 moles).

7 0
3 years ago
Write the formula for potassium oxide. why do you not need prefixes in the name ​
Molodets [167]

Potassium oxide: K₂O.

There's no need for prefixes since K₂O is an ionic compound.

<h3>Explanation</h3>

Find the two elements on a periodic table:

  • Potassium- K- on the left end of period four.
  • Oxygen- O- near the right end of periodic two.

Elements on the bottom-left corner of the periodic table are metals. Those on the top-right corner are nonmetals.

  • Potassium is a metal,
  • Oxygen is a nonmetal.

A metal and a nonmetal combine to form an ionic compound. Potassium oxide is likely to be an ionic compound. It contains two types of ions:

  • Potassium ions: Potassium is group 1 of the periodic table. It is an alkaline metal. Like other alkaline metals such as sodium Na, potassium K tends to lose one electron and form ions of charge +1 in compounds. The ion would be K⁺.
  • Oxide ions from oxygen: Oxygen is the second most electronegative element on the periodic table. It tends to gain two electrons and form the oxide ion \text{O}^{2-} when it combines with metals.

The two types of ions carry opposite charges. They shall pair up at a certain ratio such that they balance the charge on each other. The charge on each \text{O}^{2-} ion is twice that on a \text{K}^{+} ion. Each \text{K}^{+} would pair up with two \text{O}^{2-}. Hence the subscript in the formula: \text{K}_{\bf 2}\text{O}.

There are two classes of compounds:

  • Covalent compounds, which need prefixes, and
  • Ionic compounds, which need no prefix.

Prefixes are needed only in covalent compounds. For instance in the covalent compound carbon dioxide \text{CO}_2, the prefix di- indicates that there are two oxygen atoms in the formula \text{CO}_2. However, there's no need for prefix in ionic compounds such as \text{K}_2\text{O}.

7 0
3 years ago
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