Monitoring chemical reactions (C5.1) | OCR GCSE Chemistry A (Gateway Science) — Higher (J248)

C5.1 Monitoring chemical reactions

Summary This topic tackles the relationship of moles to the concentration of a solution and the volume of a gas. It also tackles the calculation of the mass of a substance in terms of its molarity. The topic then moves on to look at using equations to make predictions about yield by calculations and to calculate atom economy. Underlying knowledge and understanding Learners should be familiar with the mole from Topic C3 and know that it measures the amount of substance. They should be familiar with representing chemical reactions using formulae and using equations.

Common misconceptions The most common problem learners’ encounter with these calculations is their lack of understanding of ratios. Also most learners think that the mole and mass are the same thing. This is reinforced by use of phrases such as ‘1 mole is 12 g of carbon, ‘1 mole is the relative atomic mass in grammes’ or ‘1 mol = 12 g C’ in teaching and in textbooks equating amount of substance to mass, portion of substance, number of particles (Avogadro’s number) or number of moles. All these phrases reinforce the idea that amount of substance is a measure of mass or a number.

Reference	Mathematical learning outcomes	Mathematical skills
$CM5.1i ☑$	$calculations with numbers written in standard form when using the Avogadro constant$

calculations with numbers written in standard form when using the Avogadro constant

provide answers to an appropriate number of significant figures

convert units where appropriate particularly from mass to moles

arithmetic computation, ratio, percentage and multistep calculations permeates quantitative chemistry

arithmetic computation when calculating yields and atom economy

change the subject of a mathematical equation

Learning outcomes	To include	Maths	Working scientifically	Practical suggestions
$C5.1a ☑ explain how the concentration of a solution in mol/dm³ is related to the mass of the solute and the volume of the solution$		$M1b$	$WS1.3c, WS1.4a, WS1.4c$	$Making standard solutions.$
$C5.1b ☑ describe the technique of titration$				$Acid/alkali titrations. (PAG C6)$
$C5.1c ☑ explain the relationship between the volume of a solution of known concentration of a substance and the volume or concentration of another substance that react completely together$	$titration calculations$	$M2a, M1c$	$WS1.3c, WS1.4a, WS1.4b, WS1.4c$
$C5.1d ☑ describe the relationship between molar amounts of gases and their volumes and vice versa$		$M1c$	$WS1.3c, WS1.4a, WS1.4c, WS1.4d, WS1.4f$	$Measurement of gas volumes and calculating amount in moles. (PAG C8)$
$C5.1e ☑ calculate the volumes of gases involved in reactions using the molar gas volume at room temperature and pressure (assumed to be 24dm³)$		$M1b, M1c$
$C5.1f explain how the mass of a solute and (Combined the volume of the solution is related to Science the concentration of the solution C3.1j)$		$M1b, M1c$	$WS1.3c, WS1.4a, WS1.4c$
$C5.1g ☑ calculate the theoretical mass of a product from a given mass of reactant.$		$M1a, M1c, M1d$	$WS1.3c$
$C5.1h ☑ calculate the percentage yield of a reaction product from the actual yield of a reaction$		$M1a, M1c, M1d$	$WS1.2a, WS1.2b, WS1.2c, WS1.2d, WS1.3c, WS2a, WS2b$
$C5.1i ☑ define the atom economy of a reaction$
$C5.1j ☑ calculate the atom economy of a reaction to form a desired product from the balanced equation$		$M1a, M1c$	$WS1.3c$
$C5.1k ☑ explain why a particular reaction pathway is chosen to produce a specified product given appropriate data$	$data such as atom economy (if not calculated), yield, rate, equilibrium position and usefulness of by-products$	$M3b, M3c$	$WS1.3c, WS1.3f$

C5.1a ☑ explain how the concentration of a solution in mol/dm³ is related to the mass of the solute and the volume of the solution

WS1.3c, WS1.4a, WS1.4c

Making standard solutions.

C5.1b ☑ describe the technique of titration

Acid/alkali titrations. (PAG C6)

C5.1c ☑ explain the relationship between the volume of a solution of known concentration of a substance and the volume or concentration of another substance that react completely together

titration calculations

WS1.3c, WS1.4a, WS1.4b, WS1.4c

C5.1d ☑ describe the relationship between molar amounts of gases and their volumes and vice versa

WS1.3c, WS1.4a, WS1.4c, WS1.4d, WS1.4f

Measurement of gas volumes and calculating amount in moles. (PAG C8)

C5.1e ☑ calculate the volumes of gases involved in reactions using the molar gas volume at room temperature and pressure (assumed to be 24dm³)

C5.1f explain how the mass of a solute and (Combined the volume of the solution is related to Science the concentration of the solution C3.1j)

WS1.3c, WS1.4a, WS1.4c

C5.1g ☑ calculate the theoretical mass of a product from a given mass of reactant.

C5.1h ☑ calculate the percentage yield of a reaction product from the actual yield of a reaction

WS1.2a, WS1.2b, WS1.2c, WS1.2d, WS1.3c, WS2a, WS2b

C5.1i ☑ define the atom economy of a reaction

C5.1j ☑ calculate the atom economy of a reaction to form a desired product from the balanced equation

C5.1k ☑ explain why a particular reaction pathway is chosen to produce a specified product given appropriate data

data such as atom economy (if not calculated), yield, rate, equilibrium position and usefulness of by-products

Monitoring chemical reactions

Next Steps

Learning Objectives