To obtain the rate of the reaction
3I-(aq) + H3AsO4(aq) + 2H+(aq) --> I3-(aq) + H3AsO3(aq) + H2O (l)
I got that the rate is
1/3 delta [I-]/ delta t = delta [H3AsO4]/ delta t
is this correct
To determine the rate of a chemical reaction, you need to consider the change in concentration of reactants or products over time. In this case, you correctly identified that the rate of the reaction can be expressed as the change in concentration of iodide ions ([I-]) with respect to time (delta t) divided by 1/3. However, your assignment of delta [H3AsO4]/delta t as the rate is incorrect.
To determine the rate expression for this reaction, you should perform a balanced chemical equation. The coefficients in front of each species indicate their stoichiometric ratios in the reaction. In this case, the coefficients are already balanced, so you can directly use them to express the rate.
The balanced chemical equation for the reaction is:
3I-(aq) + H3AsO4(aq) + 2H+(aq) --> I3-(aq) + H3AsO3(aq) + H2O (l)
From the balanced equation, you can see that the ratio of I- to H3AsO4 is 3:1. Therefore, the rate expression for this reaction is:
Rate = -1/3 * (delta [I-] / delta t) = (delta [H3AsO4] / delta t)
The negative sign represents the consumption of I- and production of H3AsO4 during the reaction.
Make sure to check the specific units of concentration and time given in your experiment and use them when calculating the rate.