IB HL CHEMISTRY - Structure 1 (stoichiometry)

What does molar mass mean?

the mass in grams of 1 mole in a substance

What is molar mass relative to?

1/12 of the mass of a C12 atom

What is the definition of empirical formula?

the simplest whole number ratio of atoms present in a molecular formula

what is the definition of molecular formula?

number and type of atom in a molecule

What is theoretical yield?

The mass of a product if all the reactants react completely, according to molar ratios in the equation

What is the equation for % yield?

actual mass/theoretical mass x 100

WHat is a limiting reactant?

reactant which is totally consumed when the reaction has finished

Why is the theretical yield never reacted? (4)

• transfer losses

• side reactions

• reaction reaches equilibrim

• reactants are impure

• reaction is slow

• more than 100% = contaminated products

What is another way to calculate experimental yield?

divide the two moles

What is atom economy?

the percentage of mass of reactants that ened up in the product we want

What is the equation for atom economy?

Molecular mass of desired product/Sum of all molecular masses of all products x 100

What is a homogeneous reaction?

reaction which only reacts gases and is uniform and all species are in the same phase

What is the VM of a gas in room temperature in dm³?

22.7

What is avogrado’s rule for gases?

the molar ratio of moles are the same as the ratio of volume in a heterogenous reaction

What is water of crystallisation?

water molecules chemically bonded in an ionic crystal

What is the equation for percentage error?

Theoretical value - experimental value/ theoretical value x 100

what is the conversion to kelvin from C

273

What is a heterogeneous species?

a reaction that contains species in different phases

what are the assumptions made for ideal gases?

• gas molecules are in constant random motion

• molecular collisions are perfectly elastic

• the volume occupied by gas molecules in negligible

• there are no attractive forces between gas molecules

• kinetic energy is directly proportional to temperature in kelvin

Why do real gases deviate from ideal gas behavior?

• low temperature - kinetic energy falls and when molecules collide, attractive forces form so the collisions are no longer elastic

• high pressure - more molecules in the space, hence the volum eof molecules is significant

what is a salt?

compound formed when H+ ion is replaced by a metal cation or positive ion