3
Q:

Which of the following group is NOT Dobereiner Triads?

 

A) Li, Na, K B) N, P Au
C) Cl, Br, I D) Ca, Sr, Ba

Answer:   B) N, P Au



Explanation:
Subject: Chemistry
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Q:

Isotopes are atoms of the same element that have different

A) numbers of neutrons B) numbers of electrons
C) numbers of protons D) atomic numbers
 
Answer & Explanation Answer: A) numbers of neutrons

Explanation:

Isotopes are variations of an element that have the same charge as the original element, but a different mass, which is caused by either more/less neutrons in the nucleus.

 

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Q:

Which two atoms form an ionic bond?

Answer

Ionic bonding is a type of chemical bond in which valence electrons are lost from one atom and gained by another.. This bond generates two oppositely charged ions.


In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively charged anion.


 


Example ::


One example of an ionic bond is the formation of sodium fluoride, NaF, from a sodium atom and a fluorine atom. In this reaction, the sodium atom loses its single valence electron to the fluorine atom, which has just enough space to accept it. The ions produced are oppositely charged and are attracted to one another due to electrostatic forces.

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0 1873
Q:

The carbon tetrachloride molecule (CCl4) is

A) a nonpolar molecule with polar bonds B) a nonpolar molecule with nonpolar bonds
C) a polar molecule with polar bonds D) a polar molecule with nonploar bonds
 
Answer & Explanation Answer: A) a nonpolar molecule with polar bonds

Explanation:

The four bonds of carbon tetrachloride (CCl4) are polar, but the molecule is nonpolar because the bond polarity is cancelled by the symmetric tetrahedral shape. Hence, making the net dipole as zero and molecule as non-polar.

 

When other atoms substitute for some of the Cl atoms, the symmetry is broken and the molecule becomes polar.

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Q:

What element behaves most like magnesium?

A) Silicon B) Strontium
C) Sulphur D) Tin
 
Answer & Explanation Answer: B) Strontium

Explanation:

We know that, Elements in the same group of the periodic table have similar characteristics.

Here Magnesium and Strontium shared some similar properties because they both belong to the same group. Sr is the chemical symbol for strontium which is a group two element; it has atomic number of 38. 

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Q:

In a compound, chemical energy is contained in the

A) bonds B) movement of the electrons
C) unbonded electrons D) nuclei of the atoms
 
Answer & Explanation Answer: A) bonds

Explanation:

chemical energy is contained in the chemical bonds between the reactants in the chemical compounds.

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Q:

What is the oxidation number of carbon in NaHCO3?

A) -4 B) -3
C) +4 D) +2
 
Answer & Explanation Answer: C) +4

Explanation:

The given compound is NaHCO3 Sodium bicarbonate which is commonly known as Baking soda.

Oxidation numbers are the charges on ions. When a neutral atom loses electrons it becomes positively charged. When a neutral atom gains electrons it becomes negatively charged.

 

Here the C represents the oxidation state of carbon in this compound. Compounds are electrically neutral, which is why we set the sum of the oxidation states equal to zero.

Sodium has a +1 oxidation state. Hydrogen has a +1 oxidation state. Oxygen has a -2 oxidation state. There are three oxygen atoms, which means the total oxidation state provided by both oxygen ions is -6. Adding up these oxidation states we get:

1 + 1 + (-6) + C = 0

-4 + C = 0

=> C = 4


This means the oxidation state of carbon in this compound is +4.

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Q:

Dry ice is nothing but

A) Solid carbon dioxide B) Baking soda
C) Gaseous carbon dioxide D) Carbon monoxide
 
Answer & Explanation Answer: A) Solid carbon dioxide

Explanation:

dry-ice1531812120.jpg image

 

Dry ice is solid form of carbon dioxide, used as a cooling agent.

 

It lower temperature than that of water ice and not leave any residue.

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Q:

Nucleic acids are polymers of

A) Nucleotides B) Aminoacids
C) Proteins D) Sugars
 
Answer & Explanation Answer: A) Nucleotides

Explanation:

Nucleic acids are polymers of individual nucleotide monomers.

Each nucleotide is composed of three parts:

a 5-carbon sugar,

a phosphate group, and

a nitrogenous base.

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