Composition by percentage

Question 1

Bicarbonate of soda formula is NaHCO3. Find the mass percentages (mass%) of Na, H, C, and O in sodium Hydrogen carbonate.

Answer 1

= mass in 1 mole/ molar mass x 100%
Find the atomic masses from the periodic table. 
22.99 - Na
1.01 - H
12.01 - C
16.00 - O

Next determine how many grams of each element are present in one mole of NaHCO3.
%mass = mass in 1 mole/ molar mass x 100%

22. 99 of Na
23. 01 of H
24. 01g of C
25. 00 ( 3x16g/mol) of O
26. 99 of Na = 27.36%
27. 01 of H = 1.2%
28. 01g of C = 14.30%
29. 00 ( 3x16g/mol) of O = 57.14%

Question 2

CaCO3 commonly known as limestone is used in the preparation of a variety of compounds. Calculate the percentage composition of each element in Calcium carbonate.

Answer 2

Atomic masses are:
40.1g
12.0g
48.0g
= 100.1g

40.1 / 100.1 = 40.1% Calcium
12/ 100.1 x 100 = 12% Carbon
48 / 100.1 x 100 = 47.9% Oxygen

Question 3

Chemical reactions

Answer 3

combination reaction
combustion reaction
decomposition reaction
displacement reaction ( single replacement reaction)
metathesis reaction ( double-replacement reaction)

Question 4

what is a combustion reaction determined by?

Answer 4

usually a hydrocarbon reacting with oxygen

Question 5

double replacement reaction

Answer 5

ab+cd = ad+cb

Question 6

the sum of the oxidation number of the atoms in a compound should equal?

Answer 6

zero

Question 7

The sum of the oxidation numbers of the atoms in an ionic species ( a species with a net charge) should__ the net charge of the ionic species.

Answer 7

equal

Question 8

The oxidation number of flourine is always

Answer 8

-1

Question 9

The sum of the oxidation numbers of all atoms in a neutral compound = __?

Answer 9

0

Question 10

Determine the oxidation number of each element in Na2SO4.

Answer 10

Is the substance elemental? No
Is the substance Ionic? Yes, because metal+non-metal = ionic
S does not have a rule. 
Na = +1
O= -2

S is 0 = (2x+1) + ( -2x4) + s
= +6

Question 11

Determine the oxidation number of each element in K2C2O4

Answer 11

K = +1
O=-2
0 = (2X1)+2C + (4X-2)
C = +3

Question 12

Determine the oxidation number of each element in Ba(NO3)2

Answer 12

Is the substance elemental? No
Is the substance ionic? Yes, metal + nonmetal.
Are there any monoatomic ions?
Yes barium ion is monoatomic
Barium(2+)
O=-2
1(+2) + 2N+6(-2) = 0

Question 13

Determine the oxidation number of each element in NF3.

Answer 13

F=-1

1N+3(-1)=+3

Question 14

Determine the oxidation number of each element in (NH4)2SO4

Answer 14

Which elements have specific rules. 
H = +1
O = -2
N = -3
S = +6

Question 15

Determine the charge on a H ion when there is non-metal attached.

Answer 15

H = +1

Question 16

Determine the charge on an H ion when there a metal attached.

Answer 16

H = -1

Question 17

Oxidation is ___, Reduction is ____.

Answer 17

OIL RIG = Oxidation is loss, reduction is gain. (of electrons)

Question 18

Oxidation ____(increases/decreases) ___ the oxidation number.

Answer 18

Oxidation increases the oxidation number.