A substance has a melting point of -10°C and a boiling point of 50°C. At room temperature (25°C), it exists in which state? MCQ with Answer and Explanation
A substance has a melting point of -10°C and a boiling point of 50°C. At room temperature (25°C), it exists in which state?
A. Liquid
B. Gas
C. Solid
D. Plasma
Answer: Option A
Solution (By JKExamLibrary)
Since the room temperature (25°C) is between its melting point (-10°C) and boiling point (50°C), the substance exists in the liquid state. If the temperature were below -10°C, it would be solid, and above 50°C, it would be gas. This is based on standard phase transition principles.
Explanation:
After each half-life, half of the remaining atoms decay. Number of half-lives n = total time / half-life = 30/10 = 3. Fraction remaining = (1/2)ⁿ = (1/2)³ = 1/8. Thus 12.5% remains. Radioactive decay follows first-order kinetics. Exam trick: fraction remaining = (0.5)^(t/T), where T is half-life. After 4 half-lives, 1/16 remains.
Explanation:
To name this alkane, find the longest continuous carbon chain, which has 4 carbons (butane). Number the chain from the end closest to the substituent to give it the lowest possible number. The methyl group is on the second carbon. Thus, the IUPAC name is 2-methylbutane. Isopentane is its common name.
Explanation:
In the electrochemical series, zinc is placed above copper, meaning it has a higher oxidation potential (is more reactive). A more reactive metal can displace a less reactive metal from its aqueous salt solution. Therefore, zinc displaces copper from CuSO4, forming ZnSO4 and depositing Cu metal. R correctly explains A.
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