Question

How many grams of \[Br\] are in \[195g\] of \[CaB{r_2}\] ?

Answer 1

Hint: In request to sort out the number of grams of bromine you get in that numerous grams of calcium bromide, \[CaB{r_2}\] , you should locate the compound's percent creation.
To do that, utilization the way that one mole of calcium bromide contains
-One mole of calcium cations, \[C{a^{2 + }}\]
-Two moles of bromide anions, \[2 \times B{r^ - }\]

Complete step by step answer:
This will be a typical subject too! The mantra you should adhere to is grams to moles, to moles, to grams. How about we stroll through that. We will take the grams of \[CaB{r_2}\] and convert it to moles. At that point from moles of \[CaB{r_2}\] , we'll convert that to moles of \[Br\] , and afterward convert THAT to grams of \[Br\] .
You can in this manner use the molar mass of calcium bromide and the molar mass of bromine to decide the number of grams of bromine you get per \[100{\text{ }}g\] of calcium bromide.
The two molar mass are
${\text{For CaB}}{{\text{r}}_2}:\;\:\;\:{M_M} = {\text{199}}{\text{.89 g mo}}{{\text{l}}^{ - 1}}$
${\text{For Br:}}\;\:\;\:\;\:\;\:\;\:\;\:{M_M} = {\text{79}}{\text{.904 g mo}}{{\text{l}}^{ - 1}}$
In this way, two moles of bromide anions for each one mole of calcium bromide will give you a percent creation of
$\dfrac{{2 \times 79.904\not{{{\text{g mo}}{{\text{l}}^{ - 1}}}}}}{{199.89\not{{{\text{g mo}}{{\text{l}}^{ - 1}}}}}} \times 100 = {\text{79}}{\text{.95% Br}}$
This implies that each \[100{\text{ }}g\] of calcium bromide will contain \[79.95{\text{ }}g\] of essential bromine as bromide cations.
All you need to do now is utilize this percent piece as a change factor to decide the number of grams of bromine you get in that \[195 - g\] test of calcium bromide
 \[195\not{{{\text{g CaB}}{{\text{r}}_2}}} \cdot \mathop {\mathop {\dfrac{{{\text{79}}{\text{.95 g Br}}}}{{100\not{{{\text{g CaB}}{{\text{r}}_2}}}}}}\limits^ \downarrow }\limits^{{\text{79}}{\text{.95% Br}}} = \left[ {156gBr} \right]\]
The appropriate response is adjusted to three sig figs.

Note: Mole percent is the rate that the moles of a specific segment are of the all-out moles that are in a combination. we utilize the molar mass of \[CaB{r_2}\] to get to moles, and utilize the addendum \[2\] to get to moles of \[Br\] from moles of \[CaB{r_2}\] , and afterward the molar mass of \[Br\] to get to grams of \[Br\] !