Question

When a sample of calcium chloride was decomposed, 21.7 g of calcium and 38.3 g of chloride were produced. What is the mass of the calcium chloride that decomposed?

Answer 1

first we start by definition
what does decomposed mean?

Answer 2

It has broke down into smaller substances..

Answer 3

Correct. It means that we separated its individual parts.

Answer 4

Second, do a balanced chemical equation (this is a very important practice)

Answer 5

CaCl2 -> Ca + 2Cl?..

Answer 6

hmm not quite

Answer 7

do you have a periodic table of elements around?

Answer 8

you're going to need to apply naming of ionic compounds and utilize ionization

Answer 9

yes, but I'm afraid I don't know how to do utilize ionization..

Answer 10

it is easy to learn it
okay let us go over it okay?

Answer 11

before we delve into the topic, do you now what valence shells and valence electrons are?

Answer 12

yes..

Answer 13

what are they?

Answer 14

Valence shells are the outermost energy levels present in the atom, and the electrons located there are called valence electrons.

Answer 15

correct

Answer 16

what are Groups and Periods?

Answer 17

groups are the columns in the periodic table while periods are the rows..

Answer 18

Correct again

Answer 19

now what is an ionic bond and what is a covalent bond?

Answer 20

an ionic bond is composed of metal and a non-metal while a covalent bond is composed of 2 non-metals..

Answer 21

do you know where the metals and non-metals are in the periodic table?

Answer 22

yes, the metals are mostly on the left side, separated from the non-metals with a staircase of metalloids..

Answer 23

awesome

Answer 24

so your problem, what type of bond is it?

Answer 25

umm, an ionic bond? ._.

Answer 26

Great, you're good

Answer 27

in an ionic bond, what type of elements that are more likely to lose and gain electrons?

Answer 28

I'm not really sure, but maybe metals are the ones which lose electrons while non-metals gain electrons..

Answer 29

your guess is correct and this is a very important in naming chemical compounds and balancing chemical equations properly

Answer 30

there is this property that we call electronegativity, that is an atom's attract electrons. In general there are different scales used, but what they have in common is that metals generally have lower electronegativity than non-metals.

So higher electronegativity attracts electrons to itself and lower electronegativity tend to lose electrons

non-metal GAINS and metal LOSES

Answer 31

got it..

Answer 32

there is yet another behavior atoms display, that is it always seek to complete its valence shells to achieve the same valence electrons of the closest NOBLE GAS. The reason for this is because of stability, and this is the reason noble gasses are not very reactive like the halogens and metals

Answer 33

so the next questions:
how many electrons must Calcium lose (since we know it is a metal and loses electrons) in order to achieve the same valence electrons as the closest noble gas?

and how many electrons must Chloride must gain to achieve the same valence electrons as the nearest noble gas?

Answer 34

umm, 2 and 1?..

Answer 35

good.

In an ION a CATION loses electrons and ANION gains electrons. So pretty much you can tell that the metals will be called the cation and non-metal anion

I will attach a basic rules for naming compounds
source: Zumdahl Chemistry 9th edition

Answer 36

GROUP IA has ions of +1 because the metals in this column tend to lose 1 electron in order to achieve the same valence electrons as the nearest noble gas
GROUP IIA has ions of +2 for the same reason

And since you said that Calcium loses two electrons to achieve an Argon-like valence electrons and Chlorine gains 1 electron to achieve an Argon-like valence electrons, it must mean that we are going to need two Chlorines to accept the electrons that Calcium lost

\[CaCl_2 \rightarrow Ca^{+2} + 2Cl^{-1}\]

Answer 37

thanks for the attachment by the way :) got it..

Answer 38

you're welcome
so I just basically added an additional information into your balanced equation earlier
it was correct, but needed more information
it is said in the rules that we name the cation first (metal), Calcium
then preceded by monoatomic anion (with -1) by taking the root and adding -ide, Chloride

Answer 39

now let us proceed with conservation of mass
the atomic mass of a molecule is the sum of its individual elements

Since we know that we have 1 Calcium and 2 Chlorines that formed into calcium chloride, it must be true that it has the sum of the two individual elements

Answer 40

what do you think?