Question

which gas will relight a glowing splint when tested?
oxygen
nitrogen
carbon dioxide
hydrogen
question 8
what indicates that a base is formed when sodium reacts with water in the presence of phenolphthalein?
it turns blue
it remains colorless
it turns red
it turns pink

Explanation:

• For the first question: Oxygen is a highly reactive gas that supports combustion. A glowing splint will relight in the presence of oxygen because oxygen provides the necessary conditions for the combustion reaction to resume. Nitrogen is generally inert and does not support combustion. Carbon dioxide is used in fire - extinguishers as it does not support combustion. Hydrogen burns with a 'pop' sound when ignited but does not relight a glowing splint in the same way as oxygen.
• For the second question: Phenolphthalein is an acid - base indicator. In acidic solutions, it is colorless. In basic solutions, it turns pink. When sodium reacts with water, the reaction is \(2Na + 2H_2O=2NaOH + H_2\uparrow\). Sodium hydroxide (\(NaOH\)) is a base. So, in the presence of phenolphthalein, the solution turns pink. It does not turn blue (which is a color change for some other indicators like litmus in basic conditions but not phenolphthalein), it does not remain colorless (as a base is formed), and it does not turn red (red is a color change for phenolphthalein in more concentrated basic solutions in some cases, but the standard color change for a base formed in this reaction with phenolphthalein is pink).

Answer:

• First question: Oxygen
• Second question: It turns pink