The reaction of Cr2O3 with silicon metal at high temperatures will make chromium metal.

2Cr2O3(s)+3Si(s) > 4Cr(l)+3SiO2(s)

The reaction is begun with 161.00 g of Si and 139.00 g of Cr2O3.

How many grams of the excess reactant is left after the reaction is complete?

122.9 g of will be left from the given masses of both reactants.

Explanation:

To calculate the moles :

According to stoichiometry :

2 moles of require 3 moles of

Thus 0.91 moles of will require= of

Thus is the limiting reagent as it limits the formation of product and is the excess reagent.

Thus (5.75-1.36) = 4.39 moles  of excess reagent.

Mass of

Thus 122.9 g of will be left from the given masses of both reactants.

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.