The concentration of FeCl₂ in an aqueous solution was determined by redox titration with K₂Cr₂O₇. The sample was first dissolved in HCl to make the solution acidic. The working reaction is shown below:

Cr₂O₇^2–(aq) + 6 Fe²⁺(aq) + 14 H⁺(aq) → 2 Cr³⁺(aq) + 6 Fe³⁺(aq) + 7 H₂O(l)

In the diagram below, theCr₂O₇^2– ions are depicted in green spheres and Fe²⁺ ions are depicted in orange spheres. In the buret, the concentration of Cr₂O₇^2– ions is 0.170 M. The volumes in the buret and the flask are the same. Calculate the concentration of the FeCl₂ in the solution and determine the percentage of the Cr₂O₇^2– that must be added in order to react with all the Fe²⁺ ions.

A student accidentally spills 600 mL of 0.300 M HCl solution on a table. Calculate the mass of Na₂CO₃ required to completely neutralize the acid. The neutralization reaction is 2 HCl(aq) + Na₂CO₃(aq) → 2 NaCl(aq) + CO₂(g) + H₂O(l).

The amount of iron in ore was determined using dichrometry wherein dichromate (Cr₂O₇^2–) is used to oxidize Fe²⁺ to Fe³⁺. The net ionic equation is as follows:

Cr₂O₇^2–(aq) + 6 Fe²⁺(aq) + 14 H⁺(aq) → 6 Fe³⁺(aq) + 2 Cr³⁺(aq) + 7 H₂O(l)

Calculate the mass percent of iron in a 0.2485 g sample of ore given that 21.41 mL of 0.0167 M Cr₂O₇^2– was used to titrate all of the Fe²⁺.

The balanced equation for the reaction of bromine, Br₂, with aqueous thiosulfate in neutral solution is Br₂(l) + 2 S₂O₃²⁻(aq) → S₄O₆²⁻(aq) + 2 I⁻(aq). How much Br₂ in grams is in a solution if 37.20 mL of 0.175 M Na₂S₂O₃ is needed to titrate the Br₂ solution?

Calculate the volume of 0.115 M K₂O solution needed to react with 150 mL of 0.200 M Ni(NO₃)₂ based on the reaction below:

K₂O(aq) + Ni(NO₃)₂(aq) → 2 KNO₃(aq) + NiO(s)

Lead (ll) nitrate and ammonium iodide react to form lead(lI) iodide and ammonium nitrate according to the following reaction:

Pb(NO₃)₂ (aq) + 2 NH₄I (aq) → PbI₂ (s) + 2 NH₄NO₃ (aq) 

How many mL of a 0.178 M ammonium iodide solution is required to react with 232 mL of a 0.355 M Lead (ll) nitrate solution? And how many moles of lead(lI) iodide are formed from this reaction?

The reaction of WCl₆ with Al at 400 °C produces black crystals of a compound containing only tungsten and chlorine. When this compound is reduced with hydrogen, it gives 0.8916 g of tungsten metal and hydrochloric acid, which is absorbed in water. Titration of the hydrochloric acid requires 92.4 mL of 0.2102 M NaOH to reach the end point. What is the empirical formula of the black tungsten chloride?