Physical Science

Practice flashcards created from the Physical Science 12 covering stellar nucleosynthesis, nuclear reactions, molecular polarity, intermolecular forces, biomolecules, collision theory, catalysts, and limiting reactant stoichiometry.

Why is the statement 'The excess reactant determines theoretical yield because some of it remains' incorrect?

Incorrect; the limiting reactant determines theoretical yield because it is consumed first

A baker needs $3$ cups flour and $2$ eggs per cake. With $14$ cups flour and $10$ eggs available, what is the best production plan?

Make $4$ complete cakes; flour limits, and $2$ cups flour plus $2$ eggs remain

If a student calculates $2.50\,mol$ of product from Reactant X and $2.50\,mol$ of product from Reactant Y, what does this indicate?

The reactants are in exact stoichiometric proportion

For $2\text{Al} + 3\text{Cl}_2 \rightarrow 2\text{AlCl}_3$, if $5.4\,g\,\text{Al}$ ($27\,g\,mol^{-1}$) and $21.3\,g\,\text{Cl}_2$ ($71\,g\,mol^{-1}$) react, which reactant is limiting?

Neither reactant is limiting (they are in exact stoichiometric proportion)

What is the scientifically accurate conclusion regarding the reaction amounts of $5.4\,g\,\text{Al}$ and $21.3\,g\,\text{Cl}_2$ in $2\text{Al} + 3\text{Cl}_2 \rightarrow 2\text{AlCl}_3$?

Neither reactant is in excess because the starting amounts are exactly stoichiometric

For $4\text{Al} + 3\text{O}_2 \rightarrow 2\text{Al}_2\text{O}_3$, if $8.0\,mol\,\text{Al}$ and $6.0\,mol\,\text{O}_2$ are mixed, which statement is true?

The reactants are in exact stoichiometric proportion

In industrial or daily-life applications, why is identifying the limiting reactant important?

To predict output and reduce waste

Which statement correctly describes the behavior of reactants in a stoichiometry problem?

The limiting reactant is consumed first

For the reaction $2\text{CO} + \text{O}_2 \rightarrow 2\text{CO}_2$, which quantity should be compared most directly to identify the limiting reactant?

The moles available divided by each reactant's coefficient

Student A calculates product from each reactant; Student B selects the reactant with the smaller coefficient. Who uses a valid method?

Student A only

What does the lower calculated product amount from two reactants identify?

The limiting reactant and theoretical yield

Why should units be written explicitly throughout a stoichiometric solution?

They help verify conversions and expose setup errors

Which physical observation best indicates that a reactant was present in excess?

Some of it remains when the reaction stops

A chemist needs $0.50\,mol$ of $\text{NaCl}$. If the molar mass of $\text{NaCl}$ is $58\,g\,mol^{-1}$, what mass is required?

$$29\,g$$

For the reaction $4\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3$, how many moles of $\text{Fe}_2\text{O}_3$ can theoretically form from $8.0\,mol\,\text{Fe}$ with excess $\text{O}_2$?

$$4.0\,mol$$

For $\text{CaCO}_3 + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2$, how many moles of $\text{CO}_2$ can form if $3.0\,mol\,\text{CaCO}_3$ reacts with excess $\text{HCl}$?

$$3.0\,mol$$

For $2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$, if $48\,g\,\text{Mg}$ is used ($\text{molar mass} = 24\,g\,mol^{-1}$), how many moles of $\text{Mg}$ are available?

$$2.0\,mol$$

Using $2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$ and $2.0\,mol$ of $\text{Mg}$, what is the theoretical yield of $\text{MgO}$ in moles?

$$2.0\,mol$$