18 Fleas live in the hairs of people and animals and feed from their hosts by biting them. In doing

I need help with these quickkk WILL GIVE BRAINLIEST PLS

DerKrebs [107]

Answer: number 2

Explanation:

8 0

3 years ago

Describe the atomic theory of atoms

alexandr402 [8]

Answer: Below

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Explanation:

The atomic theory is that all matter is made up of tiny units or particles called atoms. This theory describes the characteristics, structure and behavior of atoms as well as the components that make up atoms. Furthermore, the theory states that all elements are made up of identical atoms.

The atomic theory is a theory in the study of chemistry that states atoms are the building blocks of matter. Atoms contain protons, neutrons and electrons. Protons, which have a positive charge, and neutrons are found in the nucleus of the atom. Electrons, which have a negative charge, orbit the nucleus.

According to the atomic theory, all elements contain atoms. The difference is the number of protons, electrons and neutrons in that atom. For instance, hydrogen contains one proton and one electron but no neutrons. Oxygen, on the other hand contains eight protons, electrons and neutrons. The difference in protons, electrons and neutrons determines the stability and the other properties of any particular element. These elements are grouped according to their atomic masses, which depend on the number of protons and neutrons in each of the atoms. Because oxygen has more protons and neutrons than hydrogen, it has a higher atomic mass.

5 0

3 years ago

How many moles of sodium carbonate are contained by 57.3g of sodium carbonate

Lady_Fox [76]

Answer:

$\boxed {\boxed {\sf 0.541 \ mol \ Na_2CO_3}}$

Explanation:

We are asked to find how many moles of sodium carbonate are in 57.3 grams of the substance.

Carbonate is CO₃ and has an oxidation number of -2. Sodium is Na and has an oxidation number of +1. There must be 2 moles of sodium so the charge of the sodium balances the charge of the carbonate. The formula is Na₂CO₃.

We will convert grams to moles using the molar mass or the mass of 1 mole of a substance. They are found on the Periodic Table as the atomic masses, but the units are grams per mole instead of atomic mass units. Look up the molar masses of the individual elements.

Na: 22.9897693 g/mol
C: 12.011 g/mol
O: 15.999 g/mol

Remember the formula contains subscripts. There are multiple moles of some elements in 1 mole of the compound. We multiply the element's molar mass by the subscript after it, then add everything together.

Na₂ = 22.9897693 * 2= 45.9795386 g/mol
O₃ = 15.999 * 3= 47.997 g/mol
Na₂CO₃= 45.9795386 + 12.011 + 47.997 =105.9875386 g/mol

We will convert using dimensional analysis. Set up a ratio using the molar mass.

$\frac {105.9875386 \ g \ Na_2CO_3}{1 \ mol \ Na_2CO_3}$

We are converting 57.3 grams to moles, so we multiply by this value.

$57.3 \ g \ Na_2CO_3} *\frac {105.9875386 \ g \ Na_2CO_3}{1 \ mol \ Na_2CO_3}$

Flip the ratio so the units of grams of sodium carbonate cancel.

$57.3 \ g \ Na_2CO_3} *\frac {1 \ mol \ Na_2CO_3}{105.9875386 \ g \ Na_2CO_3}$

$57.3 } *\frac {1 \ mol \ Na_2CO_3}{105.9875386 }$

$\frac {57.3 }{105.9875386 } \ mol \ Na_2CO_3$

$0.5406295944 \ mol \ Na_2CO_3$

The original measurement of moles has 3 significant figures, so our answer must have the same. For the number we found that is the thousandth place. The 6 in the ten-thousandth place to the right tells us to round the 0 up to a 1.

$0.541 \ mol \ Na_2CO_3$