Consider the reaction 2 HCl(a q)+Ba(OH)2(a q) ⟶BaCl2(a q)+2 H2 O(l) ΔH=-118 kJ Calculate the hea

step 1 So here, we're given this reaction of HCL and barium hydroxide. It's 2HCL plus barium hydroxide

Consider the reaction 2 HCl(a q)+Ba(OH)2(a q) ⟶BaCl2(a q)+2...

Consider the reaction $$2 \mathrm{HCl}(a q)+\mathrm{Ba}(\mathrm{OH})_{2}(a q) \longrightarrow \mathrm{BaCl}_{2}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l) \Delta H=-118 \mathrm{kJ}$$ Calculate the heat when $100.0 \mathrm{mL}$ of $0.500 \mathrm{M}$ HCl is mixed with $300.0 \mathrm{mL}$ of $0.100 M \mathrm{Ba}(\mathrm{OH})_{2} .$ Assuming that the temperature of both solutions was initially $25.0^{\circ} \mathrm{C}$ and that the final mixture has a mass of $400.0 \mathrm{g}$ and a specific heat capacity of $4.18 \mathrm{J} /^{\prime} \mathrm{C} \cdot \mathrm{g},$ calculate the final temperature of the mixture.

Key Concepts

Specific Heat Capacity

Specific heat capacity is the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius. This property is used in calorimetry to convert the energy transferred during a reaction into a measurable temperature change in the system, allowing for the accurate determination of the heat absorbed or released.

Energy Conservation

The law of energy conservation states that energy cannot be created or destroyed, only transformed from one form to another. In the context of calorimetry and chemical reactions, it means that the total energy released by the reaction (adjusted for the limiting reactant) is equal to the energy gained by the solution, leading to a calculable increase (or decrease) in temperature.

Calorimetry

Calorimetry is the measurement of the heat exchanged in chemical reactions or physical changes. It involves using a calorimeter, where the known mass and specific heat capacity of the system allow for the calculation of temperature changes as energy is absorbed or released, thus linking chemical energy changes with thermal energy changes.

Enthalpy Change

Enthalpy change (?H) represents the heat absorbed or released during a chemical reaction at constant pressure. In exothermic reactions, a negative ?H indicates that heat is released to the surroundings, which has implications for the thermal energy available to affect the temperature of the reaction mixture or surrounding environment.

Limiting Reactant

The limiting reactant is the substance that is completely consumed in a chemical reaction, thereby determining the maximum amount of product that can be formed. Identifying the limiting reactant by comparing the mole ratios of the reactants relative to the equation’s requirements is essential, as it directly influences the overall heat evolved or absorbed during the reaction.

Reaction Stoichiometry

Reaction stoichiometry involves using the balanced chemical equation to determine the molar relationships between reactants and products. This concept is crucial in calculating the number of moles that participate in the reaction, which forms the basis for predicting reaction yields and for performing subsequent quantitative calculations involving energy changes and concentrations.

Transcript

00:01 So here, we're given this reaction of hcl and barium hydroxide.

00:03 It's 2hcl plus barium hydroxide will form some products.

00:12 Actually, doesn't matter here.

00:13 But most importantly, it's going to give off 118 kilojoules per mole of reaction.

00:19 And so i'm going to make a quick point here.

00:22 That's going to be very important later on.

00:23 This is per mole of reaction, which is to say, for every 2 moles of hcl that we have react, we're only getting 118 kilojoules per mole.

00:32 So don't mix that up.

00:34 We'll need that information later.

00:35 And so the basic premise of this problem is that we have a certain amount of hcl and baryan hydroxide react.

00:43 We need to figure that amount out so that from that amount we can figure out how much heat is released.

00:49 And then using that the amount of heat is released, we're going to use that as q, which equal to mc delta t for the solution outside of basically the solution.

00:59 That the reaction is taking place and you can still do this calculation we're going to know q we know the mass we know this specific heat we'll find the change in temperature so first step is really stoichiometry figuring out the limiting reagent and so i'm going to erase this our first step is to figure out which of these two reagents do we have less of or which one's going to be the limiting one so for our hcl you have a point one liter hundred mil liters but just dividing right away times 0 .5 molar solution but that's moles per liter remember and so our leaders units cancel out we have 0 .05 moles of hcl for the barium hydroxide we have 0 .3 liters times 0 .1 mole per liter so our leaders units cancel out and we find that we have 0 .03 moles of barium hydroxide but here's you have to be careful.

02:05 You might think, oh, well, we have less barium hydroxide.

02:08 That's our limiting reagent.

02:10 Not exactly.

02:11 Because look at the psycheometry.

02:13 For every mole of reaction of barium hydroxide, we would need two moles of hcl.

02:18 And so to react at this 0 .03 moles of barium hydroxide, we would need twice as many moles with that of hcl.

02:24 That would be 0 .06...

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