Question

mixing baking soda and vinegar makes the temperature of the solution decrease and release carbon dioxide. which conclusion about this investigation is not valid? new elements were formed. a chemical reaction took place. the procedure caused a gas to be formed. mixing the chemicals caused them to absorb heat.

Explanation:

• When baking soda (sodium bicarbonate, \(NaHCO_3\)) reacts with vinegar (acetic acid, \(CH_3COOH\)), the reaction is \(NaHCO_3+CH_3COOH = CH_3COONa + H_2O+CO_2\uparrow\). This is a chemical reaction (so the statement “A chemical reaction took place” is valid).
• Carbon dioxide (\(CO_2\)) gas is formed (so the statement “The procedure caused a gas to be formed” is valid).
• The temperature of the solution decreases, which means the reaction absorbs heat (so the statement “Mixing the chemicals caused them to absorb heat” is valid).
• In a chemical reaction, new compounds are formed, not new elements. Elements are the basic building - blocks and are not created or destroyed in a chemical reaction (so the statement “New ELEMENTS were formed” is not valid).

Answer:

A. New ELEMENTS were formed.