We are asked to calculate the concentration of lactic acid in one cup of sour milk (assuming the rule of thumb applies), in units of mol/L.

**The rule of thumb in baking is that 1/2 teaspoon of baking soda is neutralized by one cup of sour milk. **

Recall that ** molarity** is the ratio of the moles of solute and the volume of solution (in liters). In other words:

$\overline{){\mathbf{Molarity}}{\mathbf{}}{\mathbf{\left(}}{\mathbf{M}}{\mathbf{\right)}}{\mathbf{=}}\frac{\mathbf{moles}\mathbf{}\mathbf{solute}\mathbf{}\mathbf{\left(}\mathbf{mol}\mathbf{\right)}}{\mathbf{liters}\mathbf{}\mathbf{of}\mathbf{}\mathbf{solution}\mathbf{}\mathbf{\left(}\mathbf{L}\mathbf{\right)}}}$

We’re given the density of baking soda is 2.16 g/cm^{3}. Recall that ** density** is given by:

$\overline{){\mathbf{density}}{\mathbf{=}}\frac{\mathbf{mass}}{\mathbf{volume}}}$

**The steps we need to do for this solution are:**

*Step 1:* Convert teaspoon (tsp) to cubic centimeters (cm^{3}) and 1 cup to liters (L).

*Step 2:* Calculate the moles of baking soda (sodium bicarbonate, NaHCO_{3})

*Step 3:* Perform a mole-to-mole comparison between lactic acid and sodium carbonate (1 mol lactic acid:1 mol sodium carbonate).

*Step 4:* Calculate the molarity of the solution.

Baking soda (sodium bicarbonate, NaHCO_{3}) reacts with acids
in foods to form carbonic acid (H_{2}CO_{3}), which in turn decomposes to water and carbon dioxide gas. In a cake batter, the CO_{2}(g) forms bubbles and causes the cake to rise.

The density of baking soda is 2.16 g/cm^{3}. Calculate the concentration of lactic acid in one cup of sour milk (assuming the rule of thumb applies), in units of mol/L. (One cup = 236.6 mL = 48 teaspoons).