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adelina 88 [10]
3 years ago
9

When Russian chemistry professor Dmitri Mendeleev published the first periodic table in 1869, he was trying to organize all know

n elements in a way that would help his students learn chemistry. Describe three features of the periodic table's organization. For each feature, identify one way that that the feature helps you understand and study the elements.
Chemistry
1 answer:
Bas_tet [7]3 years ago
6 0
The features of Mendeleev's periodic table which helped us to understand whole periodic table was:

1) Atomic masses. - He arranged all the known elements in increasing order of their atomic mass, atomic mass is quite similar to atomic number (just plus number of neutrons) so, he did from simpler to complex elements, so he sorted his table.

2) Formation of oxides. - He checked for the formation of oxides, and the elements which can form similar oxides, he placed them in a same family (group)

3) Assumed for unknown element. - He just left the place for unknown element, it was the application of other two concepts which i described above, specific atomic mass with no oxides, would create an empty place. So, he just assumed, that element will be discovered in future & he had to left the place.

Hope this helps! 
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Give two examples of an ionic compound. Chemical name and chemical structure.
Papessa [141]
NaCl (Sodium chloride)
LiF (Lithium fluoride)
4 0
3 years ago
The acid dissociation constant Ka of boric acid (H3BO3) is 5.8 times 10^-10. Calculate the pH of a 4.4 M solution of boric acid.
madam [21]

Answer: The pH of a 4.4 M solution of boric acid is 4.3

Explanation:

H_3BO_3\rightarrow H^+H_2BO_3^-

at t=0  cM              0             0

at eqm c-c\alpha        c\alpha          c\alpha  

So dissociation constant will be:

K_a=\frac{(c\alpha)^{2}}{c-c\alpha}

Give c= 4.4 M and \alpha = ?

K_a=5.8\times 10^{-10}

Putting in the values we get:

5.8\times 10^{-10}=\frac{(4.4\times \alpha)^2}{(4.4-4.4\times \alpha)}

(\alpha)=0.000011

[H^+]=c\times \alpha

[H^+]=4.4\times 0.000011=4.8\times 10^{-5}M

Also pH=-log[H^+]

pH=-log[4.8\times 10^{-5}]=4.3

Thus pH of a 4.4 M H_3BO_3 solution is 4.3

3 0
4 years ago
Which of the following are strongly hydrogen bonded in the liquid phase? A) nitrilesB) esters C) secondary amides D) acid chlori
-Dominant- [34]

Answer: Option (C) is the correct answer.

Explanation:

Chemical formula of a secondary amide is R'-CONH-R, where R and R' can be same of different alkyl or aryl groups. Here, the hydrogen atom of amide is attached to more electronegative oxygen atom of the C=O group.

Therefore, the hydrogen atom will be more strongly held by the electronegative oxygen atom. As a result, there will be  strongly hydrogen bonded in the liquid phase of secondary amide.

Whereas chemical formula of nitriles is RCN, ester is RCOOR' and acid chlorides are RCOCl. As no hydrogen bonding occurs in any of these compounds because hydrogen atom is not being attached to an electronegative atom.

Thus, we can conclude that secondary amides are strongly hydrogen bonded in the liquid phase.

6 0
4 years ago
Convert 213.62 grams of xenon gas at STP to L.
jolli1 [7]

Answer: The coefficient is 3.645

The exponent is 1

There are 4 significant digits

The rightmost significant figure is 5

Explanation:

Scientific notation is defined as the representation of expressing the numbers that are too big or too small and are represented in the decimal form with one digit before the decimal point times 10 raise to the power.

For example : 5000 is written as 5.0\times 10^3

According to avogadro's law, 1 mole of every gas contains avogadro's number 6.023\times 10^{23} of particles, occupy 22.4 L at STP and weighs equal to its molecular mass.

131.29 g of Xe occupy = 22.4 L at STP.

Thus 213.62 g of Xe occupy = \frac{22.4}{131.29}\times 213.62=36.45L at STP.

Scientific notation = 3.645\times 10^1L

The coefficient is 3.645

The exponent is 1

There are 4 significant digits

The rightmost significant figure is 5

4 0
3 years ago
This chemical equation represents a chemical reaction.
Strike441 [17]

Explanation:

products are Nacl + H20

5 0
3 years ago
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