WS 2.3- Salinity & the Rule of Constant Composition

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 / a.  Only NaCl
67.3g NaCl / b.  Only Table Salt
24.07g NaCl / c.  Any number of molecules that contain both positive and negative particles
19.7g NaCl / d.  KCl

2.  Why are the oceans salty and not most lakes and streams?

13.6g MgSO4 / a.  The oceans contain water that has ran over lot of land and weathered lots of rock
11.8g MgSO4 / b.  As water falls to the earth and picks of salts from the air
2.81g MgSO4 / c.  A and b are correct
8.7g MgSO4 / 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 / a.  Around 40g
0.33g Na2HCO3 / b.  Around 35g
3.7g Na2HCO3 / c.  Around 30g
5.8 Na2HCO3 / d.  Around 25g

4.  All of the following physical characteristics of ocean water will change as you get deeper and deeper except:

32.5g MgCl2 / a.  The temperature
10.2g MgCl2 / b.  The salinity
7.5g MgCl2 / c.  The density
3.38g MgCl2 / d.  The proportions of ions that make up salt

5.  Where do the ions contained in salt water come from?

8.6 SrCl2 / a.  Weathered rock
1.7 SrCl2 / b.  Volcanic emissions
0.45 SrCl2 / c.  All of the above
12.0 SrCl2 / d.  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 / % Ion in Marianas Trench Sample / % Ion in Surface Water Sample
Chloride (-1) / 58.03 / 57.03
Sodium (+1) / 27.59 / 28.59
Sulfate (-2) / 6.68 / 6.58
Magnesium (+2) / 4.68 / 4.78
Calcium (+2) / 2.18 / 1.18
Potassium (+1) / 0.11 / 1.11
Bicarbonate (-1) / 0.41 / 0.4
Bromide (-1) / 0.19 / 0.2
Borate (-1) / 0.08 / 0.06
Strontium (+1) / 0.04 / 0.06
Fluoride (-1) / 0.003 / 0.004
Other / 0.001 / 0.0001
Water characteristics / Salinity of water = 38ppt Water temperature = 4oC / Salinity of water = 33ppt
Water temperature = 22oC

6.  The fact that the two ion % are similar supports which of the following:

12.1 g KCl / a.  The Rule of Oceanic Salt
5.0g KCl / b.  The average salinity of ocean water is 35ppt
1.125g KCl / c.  The Rule of Constant Proportions
2.5g KCl / d.  Warm water is less dense

7.  The temperature and salinity data supports which of the following statements?

1.125g CaSO4 / a.  Cold salty water is more dense and sinks
3.5g CaSO4 / b.  Cold fresh water is more dense and sinks
12.7g CaSO4 / c.  Warm salty water is more dense and sinks
7.0g CaSO4 / d.  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 =