Lab Quiz weeks 3-4

specific gravity

ratio of mass of a substance to mass of an equal volume of water

specific gravity of water

1

assigned units for specific gravity when using metric system

g/mL

what is specific gravity used for?

converting volume to weight and weight to volume

when given a volume in mL, how do you convert it to weight in g?

multiply volume by specific gravity (g/mL)

when given a weight (g) how do you convert to volume (mL)?

divide by specific gravity (g/mL)

what does percent mean?

“in a hundred”

what does a percentage mean?

rate per hundred

units for percentage preparations

g and mL

what does w/v% mean?

# g in 100 mL

a way to express the concentration of a solution

• indicates mass of solute (g) present in a specific volume of solution (mL)

what does a 1% w/v solution mean?

there is 1 gram of solute in every 100 milliliters of the solution

what does v/v% mean?

# mL in 100 mL

measure of concentration that expresses the ratio of the volume of a solute to the total volume of the solution, multiplied by 100

• commonly used for liquid solutions where both the solute and solvent are liquids

what does a solution that is 70% v/v ethanol mean?

there are 70 mL of ethanol in every 100 mL of the solution

what does w/w% mean?

# g in 100 g

expresses the concentration of a substance in a mixture based on the weight of the solute relative to the total weight of the solution

• Specifically, it indicates how many grams of solute are present in every 100 grams of the total mixture

what does it mean if a solution has a concentration of 10% (w/w)?

there are 10 grams of solute in 100 grams of the solution

define percentage preparation

calculating the % strength given the amt of drug and the total qty of the preparation

amt of drug/total qty x100 = %

purpose of percentage preparations

to calculate the amt of drug given the percentage strength and the total quantity of the prescription

how do you calculate the amt of drug given the percentage strength and total qty of the prescription?

percentage (as decimal) x total qty = total amt of drug

what is the diff b/w dissolving/incorporating something and using something to make a sufficient quantity?

if dissolving/incorporating, this amount must be added to the total (denominator)

• don’t need to do this for qs

how do you convert from w/w% to w/v%?

multiply % by specific gravity

how do you convert from w/v% to w/w%?

divide % by specific gravity

• uncommon in real world

ratio strength

expresses concentration of weak compounds

• designated as 1 : X (1 part drug to X parts total compound)

define mg%

# mg drug in 100 mL of solution

• used mainly for conc. of drug in the blood, glucose, cholesterol

• always label as mg %

parts per million

# grams or mL of drug per one million grams or mL of product

• used for very dilute solution like fluoride in drinking water

dilutions are _________ proportions

inverse

amount of drug remains ________ in dilutions

constant

in a dilution, as total qty changes, the concentration of drug changes with…

the addition or removal of solvent

standard dilution equation

Q1C1 = Q2C2

concentrated acids are measured as _____

w/w%

when a concentrated acid is diluted (qs’d w water to a desired volume) it becomes ______

w/v%

equation for concentrated acids

Q_conc (C_w/w%) (sp gr) = Q_dilute (C_w/v%)

2 types of alligation

1. alligation medial

2. alligation alternate

define alligation

method of solving problems that involves the mixing of solutions or mixtures of solids possessing diff percentage strengths

alligation medial

method by which the weighted avg percentage strength of a mixture of 2+ substances of known quantity and concentration may be easily calculated

equation for alligation medial

sum (% strength x qty) / total qty = %

alligation alternate

method used to determine the qtys of ingredients of differing strengths needed to make a mixture of a desired strength

• uses matching pairs to solve for ratio of “parts” for the prescription placed on a working diagram