Calculations II

Question 1

(NS) normal saline =

Answer 1

0.9% (w/v) NaCl

Question 2

1/2 NS

Answer 2

0.45% (w/v) NaCl

Question 3

D5W

Answer 3

5% (w/v) dextrose in water

Question 4

D20W

Answer 4

20% (w/v) dextrose in water

Question 5

% w/v =

Answer 5

g / 100mL (solid mixed into a liquid)

Question 6

% v/v =

Answer 6

mL / 100mL (liquid mixed into a liquid)

Question 7

% w/w =

Answer 7

g / 100g (solid mixed into a solid)

Question 8

Ratio Strength:

Express 0.04% as a ratio strength:

step 1) 0.04 = 1 part

                                                     0.04 step 2)      0.04% ------->            \_\_\_\_\_\_\_\_\_
                                                     100

Step 3) Set up problem: 0.04/100 = 1 part/x parts

step 4) Solve for x x = 2500

*Step 5) put in appropriate form ——-> ratio strength is 1:2500

Answer 8

Ratio Strength is 1 part of some number of other parts.

Question 9

Express 1:4000 as a percentage strength:

Step 1: 1 part / 4000 parts

Step 2: Set up to solve for percentage “100”

1 part / 4000 parts = x / 100

Step 3: solve for x ————-> x = 0.025%

Answer 9

Another way to solve problem:

Express 1:4000 as a percentage strength:

1) Take 4000 / 100 = 40

2) Then divide 1/40 = 0.025

Question 11

PPM = Parts Per Million

part / 1,000,000 parts

Question 12

Express 0.00022% (w/v) as PPM

remember- set up what we know:

0.00022 g / 100mL = x parts / 1,000,000

solve for x:

X = 2.2 PPM

Answer 12

Quick TIP:

If going from: percentage strength ———> PPM

Then move decimal point to the right 4 places*

Question 13

Express 5 PPM of iron in water as a percentage

5 parts / 1000000 = X g / 100 mL

X = 0.0005%

Answer 13

Quick TIP:

If going from PPM ———–> percentage strength

Then move decimal point to the left 4 place*

Question 15

Specific Gravity equation:

2) What is Specific Gravity (SG)?

Answer 15

SG = weight of the substance (g) / weight of equal volume of water (g)

OR more simply ***SG = g / mL

2) SG is the ratio of the density of a substance to the density of water

Question 16

Water has a specific gravity of _____. Which means _

Answer 16

1

1gram water = 1 mL water

Question 17

Substances with a specific gravity < 1 are ____________ than water

Answer 17

lighter

Question 18

Substances with a specific gravity > 1 are _________ than water

Answer 18

heavier

Question 20

Dilution AND Concentration:

Q1 x C1 = Q2 x C2

Q1 = old quantity
C1 = old concentration
Q2 = new quantity
C2 = new quantity

Answer 20

Make sure Units match on both sides!!

Question 21

It the prescription calls for an ingredient that is PURE, the concentration is _______

Answer 21

100%

Question 22

A diluent, (e.g. petrolatum, lanolin, alcohol, ointment base, lactose, Aquaphor) does NOT contain any drug - the concentration of the diluent is _________

Answer 22

0%

Question 24

Alligation:

Answer 24

Is used to obtain a new strength (percentage) that is between two strengths the pharmacist has in stock.

It is used when the problem deals with 3 concentrations

Question 25

Setting up an Alligation Problem:

1) Higher % goes up higher: Top left

2) Lower % goes down lower: Bottom left

3) Desired % in the middle

4) Subtract diagonally along the X lines to obtain the number of parts. *(no negative signs on the right side of X)

5) For some problems, it will be necessary to add up the total number of parts

Answer 25

Higher % _____ parts of Higher% Xg
- =
Desired %
- =
Lower % _____ parts of Lower% Xg

Question 27

Osmolarity:

equation:

Answer 27

• is a measure of the total number of particles (or solutes) per Liter of a solution = mOsmol/L

mOsmol/L = ( weight (g/L) / MW (g/mole) ) x (# of particles) x 1000

Question 28

The number of particles in a given solution is directly proportional to its ___________.

The particles are usually measured in ___________

Answer 28

osmotic pressure

milliosmoles (mOsmol)

Question 29

Number of dissociation particles for:

Dextrose is

Answer 29

1

Question 30

Number of dissociation particles for

Mannitol is

Answer 30

1

Question 31

Number of dissociation particles for

potassium chloride (KCl) is

Answer 31

2

Question 32

Number of dissociation particles for

sodium chloride (NaCl)

Answer 32

2

Question 33

Number of dissociation particles for

sodium acetate (NaC2H3O2) is

Answer 33

2

Question 34

Number of dissociation particles for

magnesium sulfate (MgSO4) is

Answer 34

2

Question 35

Number of dissociation particles for

Calcium chloride (CaCl2) is

Answer 35

3

Question 36

Number of dissociation particles for

sodium citrate (Na3C6H5O7)

Answer 36

4

Question 37

Isotonicity:

• when solutions are prepared, the solutions used in humans must match the tonicity of body fluid as closely as possible.
• body fluids are isotonic [osmotic pressure similar to normal saline (0.9% NS)]

Answer 37

E = (58.5) (i) / (MW of drug) (1.8)

i = dissociation factor based on number of dissociated ions

The E-value is something pharmacists use to figure out how much different products to use when compounding a particular drug to make it isotonic.

Question 38

isotonicity is desired when preparing _______

Answer 38

eye drops and nasal solutions

Question 39

The relationship between the amount of drug that produces a particular osmolarity and the amount of sodium chloride that produces the same osmolarity is called the ______________

Answer 39

“sodium chloride equivalent” or E-value

Question 40

moles AND millimoles:

moles =

mmols =

Answer 40

moles = g / MW

grams of a substance divided by the MW

mmols = mg / MW

• a millimole (mmol) is 1/1000 of the molecular weight (MW)

Question 41

Milliequivalents:

mEq =

Answer 41

mEq = mg x valence / MW

mEq = mmols x valence