Why they call it "Periodic Table"?

2 answers:

4 0

Scientists finally found the reason for the periodicity of the elements: Valence electrons. And so the table became known as the Periodic Table

sesenic [268]3 years ago

4 0

The periodic table has rows running left to right and colums running up and down.

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H2SO4 is added to a large beaker of water. How is the solution different from the original water?

Natasha_Volkova [10]

Answer is: A) The solution turns blue litmus to red.

Sulfuric acid (H₂SO₄) is a strong acid, it means that the solution of sufuric acid is more acidic (pH<7) than water (pH = 7).

Chemical dissociation of sulfuric acid in water:

H₂SO₄(aq) → 2H⁺(aq) + SO₄²⁻(aq).

When solution turns phenolphthalein pink, it means it is basic (pH>7).

Sulfuric acid has more hydrogen ions (H⁺) and less hydroxide ions (OH⁻) than water.

5 0

3 years ago

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Researchers want to determine the best temperatures for storing batteries. Describe a possible experiment and list the variables

Andrew [12]

How about putting one battery in the freezer while putting another by a radiator or something that gives off heat. Leave them for an hour, then place them in an object that uses batteries and time how long it takes for it to die: Note: It may take many hours for the battery to fully deplete.

4 0

3 years ago

Covalent bonds usually occur between atoms that have

marta [7]

Answer: A: high ionization energies; high electron affinitlies.

Explanation: Covalent bonds are basically about sharing of electrons between two atoms to achieve that stable structure. They are formed between two atoms when both have similar tendencies to attract electrons to themselves (i.e., when both atoms have identical or fairly similar ionization energies and electron affinities). Covalent bonding usually occurs between two non-metals.

For effective and proper bonding, the two atoms involved in the covalent bonding exercise should be small and hungry for electrons. This is to enable the nuclei of both atoms to effectively attract and hold the shared electron(s) in place; hence, the need for high ionization energies & high electron affinities for a more effective covalent bonding.

7 0

3 years ago

Determine the limiting reactant (lr) and the mass (in g) of nitrogen that can be formed from 50.0 g n2o4 and 45.0 g n2h4. some p

Licemer1 [7]

N2O4(l) + 2 N2H4(l) → 3 N2(g) + 4 H2O(g)
1) to calculate the limiting reactant you need to pass grams to moles.
 moles is calculated by dividing mass by molar mass

mass of N2O4: 50.0 g
molar mass of N2O4 = 92.02 g/mol
molar mass of N2H4 = 32.05 g/mol.
mass of N2H4:45.0 g

moles N2O4=50.0/92.02 g/mol= 0,54 mol of N2O4
moles N2H4= 45/32.05 g/mol= 1,40 mol of N2H4

 2)
By looking at the balanced equation, you can see that 1 mol of N2O4 needs 2 moles of N2H4 to fully react . So to react 0,54 moles of N2O4, you need 2x0,54 moles of N2H4 moles
N2H4 needed = 1,08 moles.
You have more that 1,08 moles N2H4, so this means the limiting reagent is not N2H4, it's N2O4. The molecule that has molecules that are left is never the limiting reactant.

3) 1 mol of N2O4 reacting, will produce 3 mol of N2 (look at the equation)
There are 0,54 mol of N2O4 available to react, so how many moles will produce of N2?
1 mol N2O4------------3 mol of N2
0,54 mol N2O4--------x
x=1,62 mol of N2

4) the only thing left to do is convert the moles obtained, to grams.
We use the same formula as before, moles equal to mass divided by molar mass.
$moles= \frac{grams}{molar mass}$ (molar mass of N2= 28)
1,62 mol of N2= mass/ 28
mass of N2= 45,36 grams

4 0

3 years ago

What volume will 0.875 moles of Kr occupy at STP

umka21 [38]

V = nRT/P = (0.875)(0.082057)(273)/(1) = 19.6 L

6 0

3 years ago