Calorimetry IB Chemistry

In Q = mcΔT, what does 'Q' stand for?

answer choices

• Energy transferred from the surroundings

• Energy transferred to the surroundings

• The enthalpy change of reaction

• The enthalpy change of the surroundings

In Q = mcΔT, what does 'm' stand for?

• The mass of reactant used

• The mass of product made

• The mass of liquid in the calorimeter

• The mass of the calorimeter

In Q = mcΔT, what does are the typical units of m?

• metres

• mm

• kg

• g

In Q = mcΔT, what does are the typical units of m?

• the specific heat capacity of the liquid in the calorimeter

• the specific heat capacity of the products

• the specific heat capacity of the products

• the specific heat capacity of the calorimeter

What is the specific heat capacity of water in Jmol^-1K^-1?

• 8.31

• 8.314

• 4.183

• 4.18

What is the density of water in gcm^-3?

• 0.100

• 18

• 1.00

• 100

In Q = mcΔT, what are the units of ΔT?

• ^oC

• K. Using ^oC will give the incorrect answer

• K, although using ^oC will give the correct numerical answer

• Joules

If ΔH = -Q/n, what is n?

answer choices

• The moles of product in the balanced chemical equation, as written

• The moles of reactant in the balanced chemical equation, as written

• The moles of whatever has stoichiometry of '1' in the equation, as written

• The total moles of reactants used in the reaction

A chemist is caluclating ΔH = -Q/n for the enthalpy change of combustion of propane.

What 'n' should be used?

• The moles of water formed through the combustion reaction

• The moles of oxygen needed for full combustion

• The moles of carbon dioxide formed

• The moles of propane burned

Answer explanation

The enthalpy change of combustion represents the heat released when one mole of a fuel combusts in excess oxygen.

ie 'heat released per mole of fuel burned'

That's why we divide by the no. of moles of fuel we've burned: to get heat released per mole

A chemist is calculating ΔH = -Q/n for the enthalpy change of neutralisation of the reaction between sulfuric acid and sodium hydroxide

What value for 'n' should be used?

What 'n' should be used?

• The moles of water formed through the neutralisation reaction

• The moles of acid

• The moles of alkali

• The total moles of salt formed

Answer explanation

The enthalpy change of neutralisation represents the heat released when one mole of water is produced through a neutralisation reaction.

ie 'heat released per mole of water formed'

That's why we divide by the no. of moles of water we've made: to get heat released per mole of water.