Airbag

Sanjeev Venkatesan
Jack Simpson
Eugenio Arenas

2/11/14

Research
The impact sensor of an airbag senses sudden deceleration, sending a signal to the airbag module kit, which then ignites a propellant, usually sodium azide (NaN3). The reaction occurs at a temperature high enough to allow sodium azide to decompose, forming nitrogen. The nitrogen causes the bag to inflate in thirty milliseconds. Impact with the driver or passenger then causes the gas molecules to escape through vents, and the pressure inside the airbag reaches atmospheric pressure within two seconds. Often a second reaction occurs, as pure sodium is highly reactive. It combines with potassium nitrate to form additional nitrogen, potassium oxide, and sodium oxide. Potassium oxide and sodium oxide then combine with silicon dioxide to form and alkaline silicate glass. These reactions essentially occur simultaneously.
2NaN3 → 2Na + 3N2
10Na + 2KNO3 → K2O + 5Na2O + N2
K2O + Na2O + SiO2 —> alkaline silicate
(http://web.bryant.edu/~ehu/h364proj/sprg_97/dirksen/airbags.html)
(http://www.scientificamerican.com/article/how-do-air-bags-work/)
(http://www.madsci.org/posts/archives/1999-08/934263277.Ch.r.html)
Car airbag

Equation
NaHCO3(s) + HC2H3O2(aq) → C2H3NaO2 + CO2(g) + H2O(l)
Volume of Bag
We found the volume of the plastic bag by filling it completely with water. We then emptied the water into a graduated cylinder.
Ideal Gas Law
Dalton’s Law: 103.6kPa (atmospheric pressure) - 2.34kPa (vapor pressure)= 101.26kPa
101.26kPa * 1atm/101.3kPa = 1.000 atm
CO2 Solubility: 0.032mol H2O * 18.02g/mol H2O * .175g CO2/100g H2O * 1mol CO2/44.01g CO2
= .0000229 mol CO2: insignificant
PV = nRT: 1.022atm (.755L) = n (.0821atm*L/mol*K) (294.5K) n = .032 mol CO2

Calculations
.032 mol HC2H3O2 * 1mL/.000833mol HC2H3O2 = 38.42 mL vinegar
.032 mol NaHCO3 * 84g/1 mol NaHCO3 = 2.688g NaHCO3
Data
Trial
Vinegar (mL)
Sodium Bicarbonate (g)
Excess