Name:________________________
Date:___________
Per:____
WS 2.3- Salinity & the Rule of Constant Composition
Directions:
Each answer below corresponds to a mass of a particular salt found in salt water, however only the correct answer has the correct
mass of that particular salt. Answering every question correct will allow you to make the proper mixture of salt, however the more
questions you answer wrong the more incorrect your final mixture of salt will be. Your job is to obtain the correct weight and types of
ions in salt water. This mixture of salts will make 1 quart of salt water at the correct salinity.
1. When you refer to salt dissolved in salt water, what are you referring to?
58.7g NaCl
67.3g NaCl
24.07g NaCl
19.7g NaCl
a. Only NaCl
b. Only Table Salt
c. Any number of molecules that contain both positive and negative
particles
d. KCl
2. Why are the oceans salty and not most lakes and streams?
13.6g MgSO4
11.8g MgSO4
2.81g MgSO4
8.7g MgSO4
a. The oceans contain water that has ran over lot of land and
weathered lots of rock
b. As water falls to the earth and picks of salts from the air
c. A and b are correct
d. Nobody knows
3. If you boiled off all the water in 1000g of salt water, how many grams of salt would you most likely end
up with?
6.4g Na2HCO3
0.33g Na2HCO3
3.7g Na2HCO3
5.8 Na2HCO3
a.
b.
c.
d.
Around 40g
Around 35g
Around 30g
Around 25g
4. All of the following physical characteristics of ocean water will change as you get deeper and deeper
except:
32.5g MgCl2
10.2g MgCl2
7.5g MgCl2
3.38g MgCl2
a.
b.
c.
d.
The temperature
The salinity
The density
The proportions of ions that make up salt
5. Where do the ions contained in salt water come from?
8.6 SrCl2
1.7 SrCl2
0.45 SrCl2
12.0 SrCl2
a.
b.
c.
d.
Weathered rock
Volcanic emissions
All of the above
Air that rain dissolves
A Marine Chemist analyses the ionic in salt water from the bottom of the Marianas Trench and compares it to a
similar analyses of surface water finds the following:
Charged Particle
Chloride (-1)
Sodium (+1)
Sulfate (-2)
Magnesium (+2)
Calcium (+2)
Potassium (+1)
Bicarbonate (-1)
Bromide (-1)
Borate (-1)
Strontium (+1)
Fluoride (-1)
Other
Water
characteristics
% Ion in Marianas Trench
% Ion in Surface Water
Sample
Sample
58.03
57.03
27.59
28.59
6.68
6.58
4.68
4.78
2.18
1.18
0.11
1.11
0.41
0.4
0.19
0.2
0.08
0.06
0.04
0.06
0.003
0.004
0.001
0.0001
Salinity of water = 38ppt
Salinity of water = 33ppt
o
Water temperature = 4 C Water temperature = 22oC
6. The fact that the two ion % are similar supports which of the following:
12.1 g KCl
5.0g KCl
1.125g KCl
2.5g KCl
a.
b.
c.
d.
The Rule of Oceanic Salt
The average salinity of ocean water is 35ppt
The Rule of Constant Proportions
Warm water is less dense
7. The temperature and salinity data supports which of the following statements?
1.125g CaSO4
3.5g CaSO4
12.7g CaSO4
7.0g CaSO4
a.
b.
c.
d.
Cold salty water is more dense and sinks
Cold fresh water is more dense and sinks
Warm salty water is more dense and sinks
Warm fresh water is more dense and sinks
How to make salt water:
Salt
Mass added
NaCl
MgSo4
Na2HCO3
KCl
CaSO4
SrCl2
MgCl2
Total Mass =