Home › WAEC WASSCE › Chemistry › Stoichiometry of Chemical Reactions › Why does a mass-to-mass stoichiometry problem ne…
Why does a mass-to-mass stoichiometry problem need more steps than a mole-to-mole one?
ABecause coefficients change when masses are used
BBecause masses must be converted to moles and back
CBecause the equation must be balanced a second time
DBecause every mass reading has to be doubled first
Answer & Solution
Correct answer: B. Because masses must be converted to moles and back
1. Coefficients in a balanced equation relate numbers of particles, so they relate moles.
2. Laboratory work measures mass, not numbers of particles.
3. So a given mass is first divided by the molar mass to reach moles.
4. The stoichiometric factor is then applied to those moles.
5. The answer is multiplied by the molar mass of the wanted substance to return to mass.
6. The coefficients themselves never change, so the first option describes nothing real.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.3 Reaction Stoichiometry_
Related questions
In the reaction between sodium and chlorine, sodium is oxidised, which means chlorine:Ordering the three ways of writing a reaction from most to least detail about ions gives:When one element appears in more than one formula on the same side of an equation, you musWhen balancing a combustion equation, an odd number of oxygen atoms on the product side isCompounds that produce hydroxide ions by chemically reacting with water, rather than by diA double arrow is used in an acid equation to indicate that the acid is:A neutralisation reaction has an acid and a base as reactants and typically produces:Sodium hydroxide is classified as a strong base because in water it: