Sulfuric acid is used in the synthesis and processing of many chemicals and meta

Question

Sulfuric acid is used in the synthesis and processing of many chemicals and metals, and it is the electrolyte in common lead-acid batteries. It is used in various strengths, ranging from concentrated (100%) to dilute; so being able to estimate its concentration from a simple measurement of specific gravity is quite useful.

Suppose you prepare a solution that is 23.0 wt% H2SO4 in water and intend to confirm the concentration by comparing the specific gravity of the solution to that available from the literature. To 77.0 g of water you carefully add 23.0 g of H2SO4 and allow the resulting mixture to equilibrate at 20°C.

(You know that rapidly adding the acid to water or water to concentrated acid can both lead to dangerous splatters of liquid.) From the component specific gravities, estimate the volumes of water and sulfuric acid that have been blended.

Vwater = ___ mL

Vsulfuric acid = ___ mL

Estimate the density of the 23.0 wt% sulfuric acid assuming that the volumes are additive. ___ g/mL

Explanation / Answer

Specific gravities at 20°C

1) From the component specific gravities, estimate the volumes of water and sulfuric acid that have been blended.

To calculate volumes of water and sulfuric acid, use the formula:

Specific gravity = mass / volume

Solve for volume:

volume = mass / specific gravity

For water (m = 77g, specific gravity = 0.998):

Vwater = 77g / 0.998

Vwater = 77.15 mL

For sulfuric acid (m = 30g, specific gravity = 1.831):

Vsulfuric acid = 30g / 1.831

Vsulfuric acid = 16.38 mL

2) Estimate the density of the 23.0 wt% sulfuric acid assuming that the volumes are additive.

Use the density formula:

density = mass / volume

The total volume (assuming they are addivite = 16.38mL + 77.15mL = 93.53mL) and the total mass = 100g

density = 100g / 93.53mL

density = 1.0692 g/mL

3) The value for 23.0 wt% sulfuric acid at 20°C is listed as 1.1626. Estimate the volume of the 23.0 wt% sulfuric acid solution prepared as described by the above process.

Use the same density formula, but now solve for volume:

volume = mass / density

For the solution (density = 1.1626 g/mL and mass = 100g) we then calculate the volume of solution:

volume = 100g / 1.1626 g/mL

volume = 86.01 mL

Extra: as you can see, the total volume of solution using the real density is 86.01mL (which is less than the volume assuming the individual component volumes are additive 93.53mL). This indicates that water and sulfuric acid experiment very strong attractions between them.

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