VCE Chemistry energetics calculations walkthrough quiz

Positive

Zero

Negative

Equal to the activation energy

Mass of the reactant fuel that is being burned in the calorimeter experiment

Molar mass of the product formed during the reaction inside the calorimeter

Mass of the limiting reagent in the reaction taking place within the calorimeter

Mass of the calorimeter water (or solution) absorbing heat

Enthalpy change for a reaction is the same whether it occurs in one step or multiple, depending only on initial and final states

The enthalpy change for a reaction depends on the particular route or pathway taken in getting from the reactants through to the final products

All chemical reactions are exothermic, so every reaction must release heat energy to its surroundings overall

The enthalpy change of a reaction is always exactly equal to the entropy change for that same reaction

$-1780$ kJ

$-445$ kJ

$+445$ kJ

$+890$ kJ

$1.67$ kJ

$6.69$ kJ

$66.9$ kJ

$33.4$ kJ

Summing the energies of the bonds in the products and subtracting the bonds in the reactants

Adding together all of the bond energies in both the reactants and the products of the reaction

Summing energies of bonds broken (reactants) minus bonds formed (products)

Multiplying the total bond energies of the molecules by the activation energy of the reaction

Lowers the overall enthalpy change $\Delta H$ of the reaction

Increases the overall enthalpy change $\Delta H$ of the reaction

Removes the products as they form to shift the position of equilibrium

Lowers activation energy without changing $\Delta H$

Zero

Negative

Always positive

Equal to the molar mass

The specific heat capacity of water varies with temperature, so a separate constant is needed each time

Bomb calorimeters are inherently inaccurate instruments, so a correction constant is applied to every result

The calorimeter itself absorbs heat alongside the contents; the constant captures that

The constant is used to artificially increase the temperature reading so the calculated heat is larger

I will now go ahead and solve this calorimetry problem step by step, doing my very best to reach the right final answer and showing as much of my working as I can manage along the way to the end.

Energetics is all about heat and the energy changes that take place during chemical reactions, and this particular question is asking me to work out one of those energy changes from the data that has been provided.

Burning a fuel releases energy as heat, and in this question that released energy warms up the water in the calorimeter, so I will use the temperature change of the water to figure out how much energy was given out.

Calculate $Q$ absorbed using $Q = mc\Delta T$, convert to mol of fuel using $n = \frac{m}{M}$, then use $\Delta H = -\frac{Q}{n}$. State the sign convention and significant figures.