The rocket baking soda / vinegar (also called “chemical rocket” or “rocket VBS”) is an experience to illustrate the principle of action / reaction and chemical reactions .
It is in a closed box, to react sodium bicarbonate and vinegar . There is a formation of a foam and a gas CO 2 which by increasing the pressure makes the cap burst, the pressure being sufficient to propel a plastic bottle to about fifty meters, which makes it a spectacular experience chemistry and fun physics.
The body of a homemade rocket usually consists of a plastic bottle, to which are attached fins and a warhead, which may possibly contain a parachute, although the altitude reached and the strength of the materials used do not normally require braking for landing.
To launch a rocket, the reaction must begin only when it is positioned on its firing point. It must therefore be able to store the vinegar and bicarbonate, then place a cap, without the reaction occurs. In practice, this is done by flipping the rocket then:
- filling it partially with vinegar;
- slipping through the neck a bag made of toilet paper, filled with bicarbonate and closed by a string that will protrude from the neck: this bag must be sized to not reach the level of vinegar;
- by pressing a cork, which both closes the bottle and pinches the string that holds the bicarbonate sachet;
- then flipping the rocket and placing it quickly at the chosen location as no firing.
The vinegar then comes into contact with the bicarbonate sachet. The latter being made of toilet paper, it quickly loses its integrity, allowing a quick reaction. The release of carbon dioxide greatly increases the pressure in the rocket, which eventually expels the plug, then the liquid, then propelling the rocket by reaction. Once the liquid is expelled, the excess gas also comes out, but given its low mass, it will have only a minor effect on the propulsion, which is essentially due to the ejection of liquid, as with a rocket to water .
Baking soda, is a pure chemical named sodium bicarbonate (NaHCO 3 ). Dissolved in water, it separates into sodium (Na + ) and bicarbonate (HCO 3 – ) ions : NaHCO 3 → Na + (aq) + HCO 3 – (aq) . Vinegar is a weakly concentrated aqueous solution of ethanoic acid (5%), composed of oxonium ions (H 3 O + ) and ethanoate ions (CH 3 COO – ): CH 3 COOH + H 2 O <-> H 3 O + (ap) + CH 3 COO– (ap) .
The reaction between baking soda and vinegar is twofold: an acid-base reaction followed by a decomposition reaction.
- The oxonium ions react with the bicarbonate ions to form a new product called carbonic acid (H 2 CO 3 ): H 3 O + + HCO 3 – → H 2 CO 3 + H 2 O
- The carbonic acid thus formed decomposes immediately into a gas, carbon dioxide (CO 2 ), and water (H 2 O): H 2 CO 3 → H 2 O + CO 2
Hence the complete reaction: NaHCO 3 (aq) + CH 3 COOH (aq) → CO 2 (g) + H 2 O (1) + CH 3 COONa (aq)