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m_a_m_a [10]
3 years ago
7

Select the keyword or phrase that will best complete each sentence about the three general rules of for drawing Lewis structures

.a. main group b. hafnium c. valence d. hydrogen e. core f. transition metal1. Draw only__the electrons. 2. Give every___element (except hydrogen) an octet of electrons. 3. Give each____two electrons.
Chemistry
1 answer:
notsponge [240]3 years ago
4 0

Answer:

1. Draw only the valence electrons.

2. Give every element main group element (except hydrogen) an octet of electrons.

3. Give each hydrogen two electrons.

Explanation:

Lewis structures are used to describe the arrangement or configurations of the valence electrons of molecules and polyatomic ions involved in electronic bonding. A Lewis structure consists of the symbols of the elements in the molecule surrounded by dots with each dot representing each of the elements valence electrons. Also, the electrons shared between two elements are shown by dots between the two elements and these electrons are known as shared electron pairs. The valence electrons on atom that is not involved in bonding is known as lone pairs.

The three general rules for drawing Lewis structures are:

1. Draw only the valence electrons. Only the valence electrons of the atoms of elements are shown since they are the only electrons involved in chemical bonding.

2. Give every element main group element (except hydrogen) an octet of electrons. The complete eight valence electrons of the noble gases is associated with their stability. Thus, the main group elements show a tendency to form enough bonds to obtain eight valence electronsmin order to achieve stability. This is known as the octet rule. However, since the maximum number of valence electrons for elements in the first period of the period table is two, the noble gas helium has completely-filled valence shell containing two electrons known as a duplet. Hydrogen belongs to the first period and is therefore an exception tomthe octet rule.

3. Give each hydrogen two electrons. Hydrogen attains a duplet structure in accordance with the structure of helium

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What are the primary chemical components present in a phosphate buffer at ph 7.4? H3po4 and po43–?
fenix001 [56]

Answer :

The correct answer for primary component of phosphate buffer at pH = 7.4 is H₂PO₄⁻ and HPO₄²⁻ .

<u>Buffer solution :</u>

It is a solution of mixture of weak acid and its conjugate base OR weak base and its conjugate acid . It resist any change in solution when small amount of strong acid or base is added .

<u>Capacity of a good buffer : </u>

A good buffer is identified when pH = pKa .

From Hasselbalch - Henderson equation which is as follows :

pH = pka + log \frac{[A^-]}{[HA]}

If [A⁻] = [HA] ,

pH = pka + log 1

pH = pKa

This determines that if  concentration of  weak acid  and its conjugate base are changed in small quantity , the capacity of  buffer to maintain a constant pH is greatest at pka .  If the amount of [A⁻] or [HA] is changed in large amount , the log value deviates more than +/-  1M and hence pH .

Hence Buffer has best capacity at pH = pka .

<u>Phosphate Buffer : </u>

Phosphate may have three types of acid-base pairs at different pka ( shown in image ).

Since the question is asking the pH = 7.4

At pH = 7.4 , the best phosphate buffer will have pka near to 7.4 .

If image is checked the acid - base pair  " H₂PO₄⁻ and HPO₄²⁻  has pka 7.2 which is near to pH = 7.4 .

Hence we can say  , the primary chemical component of phosphate buffer at pH = 7.4  is H₂PO₄⁻ and HPO₄²⁻  .


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Answer:

346 hope this is helpfull

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