Question

Select the equation or relationship that can be used to determine the change in internal energy of the surroundings.

Predict the identity of the precipitate that forms when aqueous solutions of BaBr₂ and KNO₃ are mixed.

Group of answer choices

there is no obvious reaction between the two reagents

Ba(NO₃)₂

KBr

BaSO₄

Which species in the reaction below undergoes reduction?

                        Fe²⁺(aq) +    Mg(s) → Fe(s) +    Mg²⁺ (aq)

If 1.85 g MgO is combined with enough 1.00 M HCl to make 100.0 mL of solution in a coffee-cup calorimeter, the temperature of the resulting solution increases from 21.3 °C to 35.7 °C. Calculate the enthalpy change for the reaction per mole of MgO. Assume that the specific heat capacity of the solution is 4.18 J/g·K, and the density of the solution is 1.00 g/mL.

Answer 1

#1. Aqueous solution of BaBr2 and KNO3 when mixed , there is no precipitation or any other chemical changes. Both halides and nitrates of both Ba and K are soluble.

Thus we can say when aqueous solutions of BaBr2 and KNO3 are mixed , there is no chemical reaction.

Option (a) there is no obvious reaction between the two reagents , is the correct answer.

#2.

Reduction = gain of electrons or decrease in the oxidation number.

In given reaction;

Fe^+2(aq) + Mg(s) >>>> Fe(s) + Mg^+2(aq)

Oxidation state of Fe is decreased from +2 to zero (in Fe(s) , thus Fe^+2 undergo reduction.