Question

You titrate 41.27 mL of 0.108 M Ca(OH)2 into 25.00 mL of citric acid (C6H307) (triprotic). What is the balanced equation and the molarity of the acid?
Select both an equation and a molarity.
CoH2O2 (aq) + Ca(OH)2 (aq) + H20 (1) + Ca(C6H507)2 (aq)
2C6H807 (aq) + 3Ca(OH)2 (aq) + 6H20 (1) + Ca3(C6H507)2 (aq)
C6H2O7 (aq) + Ca(OH)2 (aq) + H20 (1) + CaC6H50% (aq)
3C6H307 (aq) + 2Ca(OH)2 (aq) + 6H20 (1) + Caz(C6H507)2 (aq)
0.267 M
0.178 M
0.0654 M
0.119 M

Answer 1

Answer:

3Ca(OH)2 + 2C6H8O7 → 6H2O + Ca3(C6H5O7)2

And 0.119M is the concentration of the citric acid.

Explanation:

In an acid-base reaction, the proton H+ and the hydroxil ion OH- reacts producing water. The ions of the acid and base (C6H5O7³⁻ and Ca²⁺ ions produce the respective salt) as follows:

Ca(OH)2 + C6H8O7 → H2O + Ca3(C6H5O7)2

To balance the Calcium ions:

3Ca(OH)2 + C6H8O7 → H2O + Ca3(C6H5O7)2

To balance the C6H5O7³⁻ ions:

3Ca(OH)2 + 2C6H8O7 → H2O + Ca3(C6H5O7)2

And to balance the oxygens of water:

3Ca(OH)2 + 2C6H8O7 → 6H2O + Ca3(C6H5O7)2

And this is the balanced reaction.

The moles of Ca(OH)2 that reacts are:

41.27mL = 0.04127L * (0.108mol/L) = 0.004457 moles Ca(OH)2

Moles of citric acid:

0.004457 moles Ca(OH)2 * (2mol C6H8O7 / 3mol Ca(OH)2) = 0.002971 moles C6H8O7

In 25.00mL = 0.02500L:

0.002971 moles C6H8O7 / 0.0250L =

0.119M