Question

name warm up sept 18th be prepared for a quiz tomorrow (sept 19th friday ). coverage: stoichiometry, limiting reagent, % yield, avogadro’s number, grams to moles, moles to grams, etc. a student has a 1 g sample of each of the following compounds: nacl, kbr, and kcl. which of the following lists the samples in order of increasing number of moles in the sample? 1. a student has a 1 g sample of each of the following compounds: alcl₃, albr₃, babr₂, bacl₂. arrange the following in order of increasing number of moles in the sample.

Explanation:

Step1: Recall molar - mass formula

The number of moles $n=\frac{m}{M}$, where $m$ is the mass and $M$ is the molar mass. Given $m = 1g$ for all samples, the number of moles is inversely proportional to the molar mass. So, we need to find the molar masses of each compound.

Step2: Calculate molar masses of $AlCl_3$, $AlBr_3$, $BaBr_2$, $BaCl_2$

The molar mass of $AlCl_3$: $M_{AlCl_3}=26.98+(3\times35.45)=26.98 + 106.35=133.33g/mol$.
The molar mass of $AlBr_3$: $M_{AlBr_3}=26.98+(3\times79.90)=26.98+239.7 = 266.68g/mol$.
The molar mass of $BaBr_2$: $M_{BaBr_2}=137.33+(2\times79.90)=137.33 + 159.8=297.13g/mol$.
The molar mass of $BaCl_2$: $M_{BaCl_2}=137.33+(2\times35.45)=137.33+70.9 = 208.23g/mol$.

Step3: Arrange in order of increasing number of moles

Since $n=\frac{m}{M}$ and $m$ is constant ($m = 1g$), the order of increasing number of moles is the order of decreasing molar mass. So the order is $BaBr_2

Answer:

$BaBr_2