Calculations Flashcards
Fill in the missing values:
What names and units go with the following prefix’s?
m
µ
n
p
k
m = milli - mmol/ml/mg
µ = micro - µ”/”/”
n = nano - nmol, ng
p = pico - pmol, pg
k = kilo - kg
By how much do the following prefixes modify an amount?
m
µ
n
p
k
m = 1/1000 or 10-3
µ = 10-6
n = 10-9
p = 10-12
k = 1000 times or 10x3
What is 1 mole of any substance?
Its molecular (or atomic) weight in grams
What triangle can be used to work out the no. of moles (include units)?
What is concentration?
What are the 2 most important ways concentration can be expressed?
What units are most commonly used?
Concentration = amount of solute dissolved, in a given amount of solvent
Weight in volume e.g. mg/ml
Weight in volume
ml or L (ml usually used for fluids)
What triangle is used when finding concentration (include units)?
What is the concentration of NaCl if 50g of NaCl is dissolved in 200ml of water?
50g –> mg = 50x1000
50000/200 = 250 mg/ml
You need to make a 40mg/ml solution of glucose. How much water is required to make this solution if you weigh out 5g of glucose?
50g -> 5000 mg
5000/40 = 125ml
If there is a 0.9% saline solution how many grams are in 100ml?
0.9g
(1% = 1g in 100ml)
What does w/v stand for?
Number of grams in a total of 100 ml of solvent
How many grams of sodium chloride are needed to make 2L of 0.9% sodium chloride?
0.9 g per 100ml
2L = 2000ml
2000 – 100 = 20
20 x 0.9 = 18g
When are dilutions used?
What do they usually combine?
When the amount of compound required is so small, it cannot be accurately measured
A volume of a solution of known concentration (stock solution) with an appropriate volume of solvent
What is the dilution factor?
Total number of unit volumes, in which your material is dissolved or how much more concentrated is one solution compared to the other
Example:
a 1 in 5 (1 in a total of 5) dilution means combining 1 volume of the solution with 4 volumes of the solvent
Dilution factor = 1:5
Dilution ratio = 1:4
Sodium chloride is maintained as a stock solution at 20 mg/ml. What is the final concentration of sodium chloride if 2 ml of stock solution is mixed with 8 ml of water?
Total volume = 2ml + 8ml = 10ml
DF = 10ml/2ml = 5ml
Final = stock / DF = 20/5 = 4mg/ml
How would you prepare 20 ml of 10mg/ml NaCl solution from a 200mg/ml stock solution?
Dilution factor = 200 mg/ml ÷ 10 mg/ml = 20
Total vol / dil. Fac = 20ml /20 = 1 ml stock
20 – 1 = 19 ml water
What is a dose?
The quantity of drug to be delivered to a patient
You need to administer 0.1 mg/kg of a drug to a 400 kg horse. You are using a solution with a concentration of 20 mg/ml. What volume do you need?
Volume? Concentration = 20 Mass = 40mg
0.1 x 400 = 40 mg
M=cxv
V = 40/20
V = 2ml
A 15 kg dog requires antibiotic capsules for 21 days. The recommended dose is 5 mg/kg every 12 h. Each capsule is 25 mg. How many tablets are needed?
75mg every 12 hours
42 x 75 = 3150mg
126 tablets
What can the rate of administering intravenous fluids can be determined from?
- volume of fluid needed
- time of administration
- number by the drops per millilitre delivered by the giving set
An animal requires 1800 ml over 24 h. Using a standard giving set (20 drops/ml). What is the drip rate?
20 drops per 1 ml
36000 drops in 24 hours
86,400 seconds in 24hours
84,400/36,400 = 1 drop every 2.4 seconds
What is the common unit used for molarity?
molar (M)
What triangle can be used to work out the molarity?
What is the amount of solute in 250ml of a 1mol.L-1 (1M) solution?
250ml = 0.25L
1mol/L x 0.25L = 0.25mol
