Question

1. when vinegar and baking soda are combined, bubbles begin to form. in this case, bubbles are evidence of a chemical reaction because they

a. pop when they are touched
b. form at a fast rate
c. show that a new gas is forming
d. are generally transparent

Explanation:

A chemical reaction is characterized by the formation of new substances. When vinegar (acetic acid, \(CH_3COOH\)) and baking soda (sodium bicarbonate, \(NaHCO_3\)) react, the chemical equation is \(CH_3COOH + NaHCO_3=CH_3COONa + H_2O+CO_2\uparrow\). The bubbles are carbon dioxide (\(CO_2\)) gas, a new substance formed in the reaction. Option A (popping when touched) is a physical property of the bubbles, not evidence of a chemical reaction. Option B (fast - forming rate) only describes the speed of bubble formation, not the nature of the reaction (a physical change could also be fast - forming). Option D (transparency) is a physical property of the bubbles. Only option C (showing a new gas is forming) indicates a chemical reaction as new substances (in this case, gas) are produced.

Answer:

C. show that a new gas is forming