Ch. 1 S And P Block Elements (Topic 13.2 And 13.3)
Questions and Answers
- 1.
The ionic radii of alkali metals will ___________ as we move down the group
- A.
Decrease
- B.
Increase
- C.
Remain same
- D.
First increase then decrease
Correct Answer
B. IncreaseExplanation
As we move down the group of alkali metals, the ionic radii increase. This is because as we move down the group, there is an increase in the number of electron shells or energy levels. The outermost electrons are further away from the nucleus, resulting in a larger atomic radius. Additionally, the increase in the number of electron shells also leads to increased shielding effect, where inner electrons shield the outer electrons from the attractive force of the nucleus, further increasing the ionic radius. Therefore, the correct answer is increase.Rate this question:
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- 2.
Why is the second ionization energy grater than first ionization energy?
- A.
Because electron is weakly held
- B.
Distance of electron from the nucleus increases
- C.
Because of inert pair effect
- D.
Because of increasing nuclear pull
Correct Answer
D. Because of increasing nuclear pullExplanation
The second ionization energy is greater than the first ionization energy because of increasing nuclear pull. This means that as an electron is removed from an atom, the remaining electrons experience a stronger attraction from the positively charged nucleus. This increased attraction makes it more difficult to remove a second electron, resulting in a higher ionization energy.Rate this question:
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- 3.
The electronegativity value of fluorine is
- A.
2
- B.
3
- C.
4
- D.
5
Correct Answer
C. 4Explanation
The electronegativity value of fluorine is 4. Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. Fluorine is the most electronegative element on the periodic table, with an electronegativity value of 4. This means that fluorine has a strong ability to attract electrons towards itself when forming a bond with another atom.Rate this question:
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- 4.
The property of alkali metals to give colouration in the burner flame has been used to detect their presence in salts by a test, known as
- A.
Slat analysis
- B.
Chemical test
- C.
Flame test
- D.
Colour test
Correct Answer
C. Flame testExplanation
The property of alkali metals to give coloration in the burner flame is utilized in the flame test. This test is used to detect the presence of alkali metals in salts. When the salt is heated in the flame, the metal ions present in the salt emit characteristic colors. Each alkali metal produces a unique color in the flame, allowing for the identification of the metal present. Therefore, the flame test is commonly used in salt analysis to identify and distinguish alkali metals.Rate this question:
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- 5.
The melting and boiling points of alkali metals are very low because of the presence of
- A.
Weak inner atomic bonds in the solid state of the alkali metals
- B.
Weak Vander Waal's forces in the solid state of the alkali metals
- C.
Weak inner ionic bonds in the solid state of the alkali metals
- D.
Weak covalent bonds in the solid state of the alkali metals
Correct Answer
A. Weak inner atomic bonds in the solid state of the alkali metalsExplanation
The melting and boiling points of alkali metals are very low because of the presence of weak inner atomic bonds in the solid state of the alkali metals. This is because alkali metals have one valence electron, which is loosely held and easily lost. As a result, the metallic bonds between atoms are weak, leading to low melting and boiling points.Rate this question:
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- 6.
The densities of alkali metals are quite low due to
- A.
The large atomic volume
- B.
The large atomic size
- C.
The large atomic radii
- D.
All of theseÂ
Correct Answer
D. All of theseÂExplanation
The densities of alkali metals are quite low because they have a large atomic volume, large atomic size, and large atomic radii. These factors contribute to the low packing efficiency of alkali metals, meaning that the atoms are more spread out and occupy a larger space. As a result, the mass of alkali metals is spread out over a larger volume, leading to lower densities.Rate this question:
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- 7.
Which alkali metal is comparitively harder?
- A.
Cs
- B.
Rb
- C.
K
- D.
Li
Correct Answer
D. LiExplanation
Li is the correct answer because it is the alkali metal that is comparatively harder. Alkali metals are known for being soft and having low hardness, but among them, Li is the hardest. This is due to its smaller atomic radius and higher ionization energy compared to the other alkali metals. These factors contribute to stronger metallic bonding in Li, making it harder than the rest.Rate this question:
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- 8.
Which alkali metal nitrate decomposes on heating?
- A.
NaNO3
- B.
LiNO3
- C.
KNO3
- D.
RbNO3
Correct Answer
B. LiNO3Explanation
LiNO3 decomposes on heating because lithium nitrate is thermally unstable and breaks down into lithium oxide, nitrogen dioxide, and oxygen gas. This decomposition reaction is exothermic and occurs at a relatively low temperature compared to other alkali metal nitrates.Rate this question:
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- 9.
Chemical formula of sodium nitrite is;
- A.
NaNO3
- B.
NaNO
- C.
NaNO2
- D.
Na2NO2
Correct Answer
C. NaNO2Explanation
The correct answer is NaNO2. Sodium nitrite is a compound composed of one sodium atom (Na) and one nitrite ion (NO2-). The chemical formula represents the elements and the ratio of atoms in the compound, and NaNO2 accurately represents the composition of sodium nitrite.Rate this question:
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- 10.
Which concentrated is used to carry out flame test?
- A.
H2SO4
- B.
HNO3
- C.
H3PO4
- D.
HCl
Correct Answer
D. HClExplanation
HCl is the correct answer because it is commonly used in flame tests. Flame tests are used to identify the presence of certain metal ions in a compound. When a metal ion is heated in the flame, it emits a characteristic color. HCl is often used as the acid to dissolve the compound and provide the metal ion for the flame test. It helps in the dissociation of the metal ion, allowing it to release energy in the form of light when heated.Rate this question:
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- 11.
Rb burns with _____________flame
- A.
Red
- B.
Reddish-violet
- C.
Lilac
- D.
Both a and b
Correct Answer
D. Both a and bExplanation
Rb (Rubidium) burns with both a red and reddish-violet flame. The color of the flame depends on the temperature and the presence of other elements. At lower temperatures, Rubidium burns with a red flame, while at higher temperatures, it produces a reddish-violet flame.Rate this question:
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- 12.
Golden - yellow flame colour is shown by;
- A.
Cu
- B.
Ba
- C.
Na
- D.
Li
Correct Answer
C. NaExplanation
The golden-yellow flame color is shown by sodium (Na). When sodium is heated, it absorbs energy and its electrons become excited. As the electrons return to their ground state, they release energy in the form of light. The specific wavelength of light emitted by sodium corresponds to the golden-yellow color. This phenomenon is utilized in flame tests to identify the presence of sodium in compounds.Rate this question:
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- 13.
Formula of barium peroxide is;
- A.
Ba2O
- B.
BaO2
- C.
Ba2O2
- D.
BaO
Correct Answer
B. BaO2Explanation
The formula of barium peroxide is BaO2. This is because the compound contains one barium ion (Ba2+) and two oxygen ions (O2-), resulting in the formula BaO2. The subscript 2 in O2 indicates that there are two oxygen ions present in the compound.Rate this question:
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- 14.
Which nitride is volatile?
- A.
Be3N2
- B.
Mg3N2
- C.
Ca3N2
- D.
Sr3N2
Correct Answer
A. Be3N2Explanation
Be3N2 is the correct answer because beryllium nitride (Be3N2) is a highly volatile compound. Volatility refers to the tendency of a substance to vaporize or evaporate at a low temperature. In the case of Be3N2, the beryllium and nitrogen atoms are held together by weak bonds, making it easier for the compound to break apart and form a gas. This high volatility makes Be3N2 more likely to exist as a gas rather than a solid at room temperature.Rate this question:
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- 15.
Which gas is evolved when metal carbonates are decomposed?
- A.
Oxygen
- B.
Hydrogen
- C.
Carbon dioxide
- D.
Nitrogen
Correct Answer
C. Carbon dioxideExplanation
When metal carbonates are decomposed, carbon dioxide gas is evolved. This is because metal carbonates contain carbon and oxygen atoms bonded together. During decomposition, the heat breaks the bonds between the carbon and oxygen atoms, releasing carbon dioxide gas as a byproduct.Rate this question:
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