1.
On of the following alkali metals is most reactive. which is that?
Correct Answer
B. Cs
Explanation
Cs (Cesium) is the most reactive alkali metal because it has the largest atomic radius and the lowest ionization energy among the options given. The larger the atomic radius, the easier it is for the outermost electron to be removed, resulting in a lower ionization energy. Cs has the largest atomic radius, making it easier for its outermost electron to be removed, thus making it the most reactive alkali metal.
2.
Elements of Group I - A give colours in flame. it is due to their;
Correct Answer
C. Single electron in the outer most orbit
Explanation
The elements in Group I-A give colors in flame due to their single electron in the outermost orbit. When these elements are heated, the outermost electron absorbs energy and jumps to a higher energy level. As the electron returns to its original energy level, it releases the absorbed energy in the form of visible light, which gives rise to the characteristic colors observed in flames.
3.
One of the following statements regarding alkali metals is not correct. indicate that.
Correct Answer
D. They form carbonates which decompose on heating
Explanation
The statement "they form carbonates which decompose on heating" is incorrect. Alkali metals do form carbonates, but these carbonates are stable and do not decompose on heating.
4.
Measure of the tendency of an atom to attract a bonding pair of electron is called
Correct Answer
C. Electronegativity
Explanation
Electronegativity is a measure of an atom's tendency to attract a bonding pair of electrons. It indicates the ability of an atom to attract and hold onto electrons in a chemical bond. It is an important concept in understanding the polarity of chemical bonds and the distribution of electrons in molecules.
5.
The atomic radii decrease as we move from left to right in a period. This is because;
Correct Answer
C. Nuclear charge increase
Explanation
The correct answer is "nuclear charge increase". As we move from left to right in a period, the number of protons in the nucleus increases. This leads to a greater positive charge in the nucleus, which attracts the electrons more strongly and pulls them closer to the nucleus. As a result, the atomic radius decreases. The other options mentioned - number of electrons increase, number of neutrons increase, and atomic number increase - do not directly affect the atomic radius in the same way as the increase in nuclear charge.
6.
The most electronegative element fluorine has electronegativity value 4. Cs is least electronegative. what is its electronegativity value?
Correct Answer
D. 0.7
Explanation
Fluorine is known to be the most electronegative element with an electronegativity value of 4. Since Cs is stated to be the least electronegative element, it can be inferred that its electronegativity value would be lower than that of fluorine. Among the given options, the closest value to being lower than 4 is 0.7. Therefore, the electronegativity value of Cs is 0.7.
7.
Silicon is a;
Correct Answer
C. Semiconductor
Explanation
Silicon is a semiconductor because it has properties of both conductors and insulators. It can conduct electricity under certain conditions, but not as well as a good conductor like copper or silver. At the same time, it can also act as an insulator and resist the flow of electricity. This makes silicon a crucial material in the field of electronics, as it can be used to control the flow of current in devices such as transistors and diodes.
8.
Sulfur burns with
Correct Answer
B. Blue flame
Explanation
Sulfur burns with a blue flame because when sulfur reacts with oxygen, it undergoes combustion and produces sulfur dioxide gas. The blue flame is an indication of a complete combustion process, where there is sufficient oxygen available for the reaction. The blue color is a result of the excitation of electrons in the sulfur molecules, which emit light in the blue region of the electromagnetic spectrum.
9.
Phosphorus burns with
Correct Answer
A. White flame
Explanation
Phosphorus burns with a white flame because when it is heated, the energy causes the electrons in the phosphorus atoms to become excited. As the electrons return to their ground state, they release energy in the form of light. The specific wavelengths of light emitted by phosphorus correspond to the color white, resulting in a white flame.
10.
What is the color of Aluminium chloride
Correct Answer
D. Pale yellow
Explanation
Aluminium chloride is pale yellow in color.
11.
The nature of metallic oxides is
Correct Answer
B. Basic
Explanation
Metallic oxides are generally basic in nature. This is because they react with water to form metal hydroxides, which are alkaline in nature. These oxides have a tendency to donate hydroxide ions (OH-) when dissolved in water, resulting in a basic solution. Examples of basic metallic oxides include sodium oxide (Na2O) and calcium oxide (CaO).
12.
Which of the trimeric formula represents sulfur tri-oxide?
Correct Answer
B. S3O9
Explanation
The correct answer is S3O9. This is because the trimeric formula for sulfur tri-oxide is represented by S3O9, which indicates that there are three sulfur atoms and nine oxygen atoms in the compound. The other options, SO3, S2O6, and S2O2, do not accurately represent the trimeric formula for sulfur tri-oxide.
13.
The formula of sodium hypochlorite is
Correct Answer
D. NaOCl
Explanation
The correct answer is NaOCl. Sodium hypochlorite is a chemical compound made up of sodium, oxygen, and chlorine. The formula NaOCl represents the correct combination of these elements. NaCl, NaClO4, and NaClO3 do not accurately represent the composition of sodium hypochlorite.
14.
Which of the following form giant covalent oxide?
Correct Answer
C. Silicon dioxide
Explanation
Silicon dioxide is a giant covalent oxide because it consists of a three-dimensional network of covalent bonds between silicon and oxygen atoms. Each silicon atom is bonded to four oxygen atoms, and each oxygen atom is bonded to two silicon atoms. This results in a strong and stable structure, making silicon dioxide a solid with a high melting and boiling point. In contrast, phosphorus (V) oxide, carbon dioxide, and sulfur trioxide do not form giant covalent structures and have different bonding arrangements.
15.
Aluminium hydroxide is ___________ in nature
Correct Answer
D. AmpHoteric
Explanation
Aluminium hydroxide is considered amphoteric because it can act as both an acid and a base. It can react with acids to form salts and water, and it can also react with bases to form complex ions. This dual nature allows aluminium hydroxide to exhibit both acidic and alkaline properties, making it amphoteric.