The question asks about the properties of long-chain compounds formed by silicon. These compounds are typically silanes, which are analogous to alkanes but with silicon atoms forming the backbone. We need to evaluate the given options based on the chemical characteristics of silicon and its compounds.
B) Very reactive — Long-chain silicon compounds (silanes) contain Si-Si bonds which are weaker than C-C bonds. This weakness makes them less stable and highly reactive, especially towards oxidizing agents and water, leading to their decomposition.
A, B, C, D, E, and F live on six different floors of the same building. The lowermost floor is numbered 1, and the topmost is numbered 6. E lives on the floor immediately below F's floor. D lives on the 2nd floor. C lives on the floor immediately below A's floor. F does not live on the 5th floor. On which floor does B live?
This is a logical reasoning problem involving arrangement. We need to determine the floor on which B lives by systematically placing the given people on the six floors based on the clues provided.
Final Arrangement (Example from Case 1):
Correct Option: B) 1 st
This problem requires us to find the approximate value of a given expression. We will use the approximation method by rounding off each number to its nearest whole number before performing the calculations. This simplifies the arithmetic and allows for a quick estimation.
Thus, the approximate value of the expression is 121.
C) 121 is the correct approximate value.
The question asks to identify a group of three elements that constitutes Dobereiner's triads. Dobereiner's law of triads states that when elements are arranged in order of increasing atomic mass, groups of three elements (triads) with similar chemical properties can be identified. In a triad, the atomic mass of the middle element is approximately the arithmetic mean of the atomic masses of the other two elements.
Let's check the atomic masses for Cl, Br, and I:
Now, calculate the arithmetic mean of the atomic masses of Cl and I:
\[ \text{Average atomic mass} = \frac{\text{Atomic mass of Cl} + \text{Atomic mass of I}}{2} \]\[ \text{Average atomic mass} = \frac{35.5 + 126.9}{2} = \frac{162.4}{2} = 81.2 \text{ amu} \]The calculated average atomic mass (\(81.2 \text{ amu}\)) is very close to the atomic mass of Bromine (\(79.9 \text{ amu}\)). Additionally, Cl, Br, and I are all halogens and exhibit similar chemical properties. Therefore, \(\text{Cl}\), \(\text{Br}\), \(\text{I}\) form a Dobereiner's triad.
To find the net percentage change, we can assume an initial salary and then apply the percentage decrease and increase sequentially. Alternatively, we can use the formula for successive percentage changes.
Let Bhuvan's initial salary be \(P = 100\).
Decrease = \(16\%\) of \(100 = \frac{16}{100} \times 100 = 16\).
Salary after decrease \(= 100 - 16 = 84\).
Increase = \(25\%\) of \[84 = \frac{25}{100} \times 84 = \frac{1}{4} \times 84 = 21\].
Final salary \(= 84 + 21 = 105\).
Net change in salary \(= \text{Final Salary} - \text{Initial Salary} = 105 - 100 = 5\).
Since the initial salary was \(100\), a change of \(5\) represents a \(5\%\) change.
As the final salary (\(105\)) is greater than the initial salary (\(100\)), it is a net increase.
Alternatively, using the successive percentage change formula:
If there are two successive percentage changes, \(x\%\) and \(y\%\), the net percentage change is given by:
\[ \text{Net Change} = \left(x + y + \frac{xy}{100}\right)\% \]Here, a decrease of \(16\%\) means \(x = -16\).
An increase of \(25\%\) means \(y = +25\).
Substitute these values into the formula:
\[ \text{Net Change} = \left(-16 + 25 + \frac{(-16) \times 25}{100}\right)\% \]\[ \text{Net Change} = \left(9 + \frac{-400}{100}\right)\% \]\[ \text{Net Change} = (9 - 4)\% \]\[ \text{Net Change} = 5\% \]Since the result is positive, it is a net increase.
C) 5% increase. The calculations show a net increase of 5% in Bhuvan's salary.
The question asks to identify the first Deputy Chairman of the Planning Commission of India. This requires knowledge of the historical appointments related to the Planning Commission.
Correct Option: B) Gulzarilal Nanda was the first Deputy Chairman of the Planning Commission of India.
The question asks to identify the institution that initiated the microfinance movement in India on a pilot basis in 1992. This requires knowledge of the history and key players in India's microfinance sector.
Correct Option: B) NABARD
The given series is 7, 18, 34, 72, 142, ?. We need to identify the pattern in the series to find the missing number. Let's analyze the relationship between consecutive terms.
The sequence of differences is 11, 16, 38, 70. This doesn't immediately reveal a simple arithmetic or geometric progression.
Let's try to find a pattern where each term is derived from the previous term using multiplication and addition/subtraction.
We observe a consistent pattern: multiply by 2, then alternately add 4 and subtract 2.
The last operation was subtracting 2. So, the next operation should be adding 4.
\[ \text{Next term} = 142 \times 2 + 4 \\ \text{Next term} = 284 + 4 \\ \text{Next term} = 288 \]D) 288 is the correct answer, as it follows the established pattern of multiplying by 2 and alternately adding 4 then subtracting 2.
The problem involves finding the image distance for an object placed in front of a concave mirror. We will use the mirror formula, which relates the focal length (\(f\)), object distance (\(u\)), and image distance (\(v\)).
Correct Option: A) 24 cm. This is the calculated image distance, and the positive sign indicates a virtual image formed behind the mirror.
A and B together can complete a work in 10 days. A alone can complete it in 20 days. If B does the work only for the first half of the day daily, then in how many days will A and B together complete the work?
15 days
\( \frac{22}{3} \) days
\( \frac{43}{2} \) days
\( \frac{40}{3} \) days
This problem involves work and time. We will first calculate the individual work rates of A and B. Then, we will determine their combined work rate under the given condition (B works only for half a day) and finally calculate the total time required to complete the work.
Calculate A's daily work rate:
A alone can complete the work in 20 days.
\[ \text{A's 1-day work} = \frac{1}{20} \]Calculate the combined daily work rate of A and B:
A and B together can complete the work in 10 days.
\[ \text{(A + B)'s 1-day work} = \frac{1}{10} \]Calculate B's daily work rate:
B's 1-day work can be found by subtracting A's 1-day work from (A + B)'s 1-day work.
\[ \text{B's 1-day work} = \text{(A + B)'s 1-day work} - \text{A's 1-day work} \] \[ \text{B's 1-day work} = \frac{1}{10} - \frac{1}{20} \] \[ \text{B's 1-day work} = \frac{2 - 1}{20} = \frac{1}{20} \]Calculate B's work rate under the new condition:
If B does the work only for the first half of the day daily, B's effective daily work is half of his full daily work.
\[ \text{B's effective 1-day work} = \frac{1}{2} \times \text{B's 1-day work} \] \[ \text{B's effective 1-day work} = \frac{1}{2} \times \frac{1}{20} = \frac{1}{40} \]Calculate the combined daily work rate of A and B under the new condition:
Now, A works for a full day and B works for half a day.
\[ \text{New (A + B)'s 1-day work} = \text{A's 1-day work} + \text{B's effective 1-day work} \] \[ \text{New (A + B)'s 1-day work} = \frac{1}{20} + \frac{1}{40} \] \[ \text{New (A + B)'s 1-day work} = \frac{2 + 1}{40} = \frac{3}{40} \]Calculate the total number of days to complete the work:
If the combined daily work is \(\frac{3}{40}\) of the total work, then the total number of days to complete the work is the reciprocal of this rate.
\[ \text{Total days} = \frac{1}{\text{New (A + B)'s 1-day work}} \] \[ \text{Total days} = \frac{1}{\frac{3}{40}} = \frac{40}{3} \text{ days} \]Correct Option: D) \( \frac{40}{3} \) days