Which of the following CANNOT be an empirical formula?
\(CH\)
\(CH_{2}\)
\(P_{2}O_{5}\)
\(N_{2}O_{4}\)
Correct answer is D
The empirical formula is always in the ratio of the smallest positive integer, hence, \(N_{2}O_{4}\) has an empirical formula \(NO_{2}\)
\(Cu\) and \(HNO_{3}\) are not suitable for preparing hydrogen gas because of their
reactivity and oxidation respectively
conductivity and corrosiveness respectively
melting point and reduction respectively
electronegativity and solubility respectively
Correct answer is A
Copper is not active enough to replace hydrogen in an acid. Also, nitric acid is a strong oxidizing agent which quickly oxidises hygrogen to water.
150\(cm^{3}\)
75\(cm^{3}\)
30\(cm^{3}\)
25\(cm^{3}\)
Correct answer is A
Using the formula, \(\frac{C_{A}V_{A}}{C_{B}V_{B}} = \frac{N_{A}}{N_{B}}\), we have
\(\frac{0.1 \times V_{A}}{0.3 \times 25} = \frac{2}{1}\)
\(V_{A} = \frac{0.3 \times 25 \times 2}{0.1 \times 1}\)
\(V_{A} = 150cm^{3}\)
Which of the following statements best explains the difference between a gas and a vapour?
Unlike gases, vapours are liquids at room temperature
Unlike gases, vapour can easily be condensed into liquids
Unlike gases, vapour is readily converted into solids
Vapours are generally denser than gases
Correct answer is B
Vapour is the equilibrium state between the gases and liquid, and it can bounce back to its original form, liquid with constant temperature and pressure exerted on it.
The water is at lower temperature than the ice
Energy is absorbed when the ice changes to water
Energy is released when the ice changes to water
The water molecules vibrate about a fixed point
Correct answer is B
Heat energy near the ice gets absorbed into the ice. The energy breaks the bonds of the ice, causing it to melt into liquid water. On other words, when ice melts, the energy gets absorbed into the water.
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