1. First, identify the physical state of matter of baking soda. Describe another property of baking soda.
<u>Baking soda is composed of sodium bicarbonate</u> which is also named sodium hydrogen carbonate, and it is a chemical compound with the formula NaHCO₃. Sodium bicarbonate is a white solid that is crystalline, but often appears as a fine powder. It is also a salt composed of a sodium cation (Na⁺) and a bicarbonate anion (HCO₃⁻).
<u>Baking soda is alkaline with a pKa of 10.329.</u> This reagent is used in baking as a leavening agent because when it reacts with acid, carbon dioxide is released causing expansion of the batter.
2. Next, identify the physical state of matter of vinegar. Describe another property of vinegar.
<u>Vinegar is an aqueous solution of acetic acid which is a colourless acid liquid organic compound with the chemical formula CH3COOH and a pKa of 4.756.</u> <u>Vinegar typically contains 5–20% by volume of acetic acid. </u>Usually the acetic acid is produced by the fermentation of ethanol or sugars by acetic acid bacteria. Vinegar also contains numerous flavonoids, phenolic acids, and aldehydes.
<u>Vinegar has a sour taste and a pungent smell because of the acetic acid.</u> This acid determines vinegar’s chemical properties. The pH of vinegar is typically in the range of 2 to 3.5, depending on the concentration of acetic acid, and it has of approximately 0.96 grams per milliliter, depending on its acidity.
3. Then, explain what Janel should see when she mixes the baking soda and vinegar.
<u>When Janel mixes the baking soda with vinegar she will observe the formation of many bubbles in the mixture due to the evolution of carbon dioxide.</u> When these ingredients are mixed, the sodium bicarbonate reacts with the acetic acid to produce carbon dioxide, water and sodium acetate according to the following reaction.
NaHCO₃(s) + CH₃COOH(l) → CO₂(g) + H₂O(l) + CH₃COONa (aq)
The carbon dioxide escapes the solution as bubbles. The bubbles are heavier than air, so the carbon dioxide collects at the surface of the container or overflows it.
4. Describe the states of matter of the new materials that are formed.
After the reaction between baking soda and vinegar, <u>a transparent liquid formed by water and aqueous sodium acetate will be obtained</u>, in addition to the evolution of <u>carbon dioxide, which is a colorless gas at room temperature.</u> However, if an excess of baking soda is added initially, a solid corresponding to the sodium bicarbonate will be observed, which did not react with the acetic acid present in the vinegar.
5. Explain how Janel can be certain a change has occurred.
Janel could make the reaction in a closed container. To make sure that the reaction occurred, Janel could unclog this container and immediately place a phosphor in the hole in it. If carbon dioxide was produced, this gas will extinguish the phosphor flame. Because CO₂ is heavier than air, it displaces it. This starves a fire of the oxygen needed for combustion.
Being that a dilute sodium acetate solution remains after the reaction, Janel could also boiled off this solution to obtained a supersaturated solution of sodium acetate. This will form a "hot ice" that will spontaneously crystallize, releasing heat and forming a solid that resembles water ice.
