Chemistry Questions

Q:

A substance that cannot be broken down into simpler substances

A) Heterogenous mixure B) Compound
C) Homogenous mixture D) Element
 
Answer & Explanation Answer: D) Element

Explanation:

A substance that cannot be decomposed (broken down) into simpler substances by ordinary chemical means.

Examples: gold, iron, carbon, hydrogen, oxygen, nitrogen.

Material composed of only one kind of matter throughout (same atoms or same molecules).

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Q:

Browning of paper in old books is caused by

A) oxidation of cellulose B) collection of dust
C) frequent use D) lack of aeration
 
Answer & Explanation Answer: A) oxidation of cellulose

Explanation:
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Q:

What is the bond order of O2?

A) 1.5 B) 2
C) 2.5 D) 1
 
Answer & Explanation Answer: B) 2

Explanation:

The number of bonds between a pair of atoms is called the bond order.

Bond orders can be calculated from Lewis structures, which are the heart of the valence-bond model. Oxygen, for example, has a bond order of two.

Structure

When there is more than one Lewis structure for a molecule, the bond order is an average of these structures. The bond order in sulfur dioxide, for example, is 1.5  the average of an S-O single bond in one Lewis structure and an S=O double bond in the other.

Structures

In molecular orbital theory, we calculate bond orders by assuming that two electrons in a bonding molecular orbital contribute one net bond and that two electrons in an antibonding molecular orbital cancel the effect of one bond. We can calculate the bond order in the O2 molecule by noting that there are eight valence electrons in bonding molecular orbitals and four valence electrons in antibonding molecular orbitals in the electron configuration of this molecule. Thus, the bond order is two.

Equation

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Q:

The process of conversion of sugar to alcohol is called

A) Moulding B) Infection
C) Fermentation D) Alcohol fixation
 
Answer & Explanation Answer: C) Fermentation

Explanation:

The process of conversion of sugar to alcohol is called Fermentation in which sugar is coverted to alcohol with the help of yeast.

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Q:

The bonds in BaO are best described as

A) covalent B) ionic
C) polar D) non polar
 
Answer & Explanation Answer: B) ionic

Explanation:

In the bond formation of barium with oxygen, the valency electrons from the barium transferred to the oxygen and forms an ionic bond.

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Q:

Which of the following is a Decomposition Reaction?

A) 2HgO ----> 2Hg + O2 B) 6NaNO3 ----> 6NaNO2 + 3O2
C) ZnCO3 ----> ZnO + CO2 D) All the above
 
Answer & Explanation Answer: D) All the above

Explanation:

All the given reactions are Decomposition reactions.

Decomposition reaction is a reaction in which only one reactant is splitted into two or more products.

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Q:

What name is given to the bond between water molecules?

A) Polar B) Polar covalent
C) Hydrogen D) None of the above
 
Answer & Explanation Answer: C) Hydrogen

Explanation:

The name given to the bond between water molecules is a hydrogen bond. These bonds occur between the slightly negative oxygen of one water molecule and the slightly positive hydrogen of another water molecule. Hydrogen bonding gives water special physical properties.

 

The differences in electronegativity between hydrogen and oxygen lead to an unequal sharing of electrons. Electronegativity measures how strongly an atom attracts electrons. Oxygen, with its higher electronegativity, pulls on the shared electrons more, giving the oxygen atom a partial net negative charge. The shared electrons spend less time with the hydrogen atoms; therefore, the hydrogen regions of water have partial positive charges.

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Q:

What types of orbital overlap occur in Cumulene?

Answer

A cumulene is a hydrocarbon with three or more cumulative double bonds. They are analogous to allenes, only having a more extensive chain. The simplest molecule in this class is butatriene, which is also called simply cumulene.


 


The carbons on the ends are sp² hybridized, with a p-orbital for the 'second' bond in the double bond with their neighboring carbons.


They have those sp² orbitals overlapping with the s from the hydrogen, and they have a p overlapping in the pi bond with the neighboring carbon. They also have a sigma bond with the neighboring carbon I'll get to.


The middle carbons each have two pi bonds with their neighbors, leaving sp hybridiaztion for the rest. So they have sp/sp² with the end carbons, and sp/sp with each other. (And they also have p/p in the pi bonds).


 


All orbital overlappings in Cumuene are :


* s/sp²


* p/p


* sp/sp²


* sp/sp

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