Lab Math
A technologist desires to prepare 125 mL of a 0.25 N HCl solution. He has a 6N concentrated solution. How much of this solution will he need?
C1V1 = C2V2
(6N)(V1) = (0.25N)(125mL)
V1 = 5.21mL of the 6N solution
This species is the most common cause of UTI's
E. coli
The purpose of the photodetector is to:
Convert transmitted radiant energy into electrical energy.
Which standard of glassware do we use in a clinical laboratory
Class A glassware
In chemistry, 32.45 rounds to:
32.4
A 0.5 M H3PO4 solution is prepared. What is its concentration in Normality?
N = (M)(Total Positive Valence of the Ions)
N = (0.5)(3) = 1.5 N
This species can cause HUS
E. coli O157:H7
Quartz cuvettes are used for applications requiring UV radiation because glass cuvettes:
Absorb light in the UV region
To contain pipettes are different from To deliver pipettes because:
To contain pipettes have you blow out the excess fluid, while the To deliver pipettes DO NOT have you blow out the excess liquid
Describe the difference between a shift and a trend
shift = an abrupt change in the mean that becomes continuous
trend = A gradual change in the mean that goes in one direction
What is the concentration in mg per deciliter of a 2.5 mEq/L Ca2+ (MW = 40) standard?
mEq/L = (mg/dL)(10)/(gew)
2.5 = (Xmg/dL)(10)/(40 ÷ 2)
X = 5mg/dL
Enterobacterales exhibit these 4 things
1. oxidase negative
2. reduce nitrate to nitrite
3. ferments glucose
4. motile except for Shigella species, Klebsiella species, and Yersinia species
A 77% T reading was obtained for a solution of a compound. What is the absorbance value?
A = 2 - log(%T)
A = 0.114
Kohler Illumination is:
Used to set baseline operation of a light microscope. Have the best optical quality with the least eye strain.
Which of the following can the machine still be run after appearing (although is not recommended)
- 1-2s
- 1-3s
- 2-2s
- 4-1s
- R-4s
- 10x bar
1-2s
A sample of blood is evaluated and found to have the following concentrations:
[ HCO3 - ] = 7.80 X 10-2M [ H2CO3 ] = 1.58 X 10–3 M
What is the pH of the blood?
pH = pKa + log([concentration of the anion of the acid]/[concentration of the unionized acid])
pKa of carbonic acid = 6.1
pH = 6.1 log([7.80 X 10-2M]/[1.58 X 10–3])
pH = 7.79
O157:H7 can be presumptively put onto these two agars to identify and has these colors.
CHROMagar O157:H7 = clear
MACsorb agar = pink
In atomic absorption spectrophotometry, the purpose of the flame is to:
form free, ground state atoms
What are the 5 things needed to produce CLRW
1. Pre-filters and Filters
2. Purification with distillation, deionization, RO, or UV
3. 0.2uM membrane
4. Mixed bed ion exchanger
5. Activated carbon
Describe the meaning of these Westgard rules:
- 1-2s
- 1-3s
- 2-2s
- 4-1s
- R-4s
- 10x bar
- 1-2s: One control observation exceeds the mean +2 SD or the mean -2 SD
- 1-3s: One control observation exceeds the mean +3 SD or the mean -3 SD
- 2-2s: Two consecutive controls exceed the mean ±2 SD
- 4-1s: Four consecutive controls exceed the mean +1 SD or four controls exceed the mean -1 SD
- R-4s: The difference between two consecutive controls is greater than 4 SD
- 10x bar: Ten consecutive controls fall on one side of the mean
35.7 mL of 1.35 M potassium hydroxide is used to titrate 12.7 mL of a sulfuric acid solution.
What is the molarity of the sulfuric acid solution?
H2SO4(aq) + 2KOH(aq) → K2SO4(aq) + 2H2O(L)
(35.7mL = 0.0357L)(1.35M) = 0.0482 moles KOH
0.0482KOH/2 = 0.0241 moles H2SO4
0.0241 moles H2SO4/(12.7mL = 0.0127L)
M = 1.90
ESBL is screened under which circumstances, and tested with which drugs?
ESBL is screened for E. coli, Klebsiella species, and P. mirabilis when Ceftriaxone is less than 25mm for AST testing, or Ceftazidime is less than 22mm for AST testing
CAZ, CAZ w/ CLA, CTX, and CTX w/ CLA is tested, look for a difference of 5mm between the one with/without CLA
An unknown sample is found to have an absorbance of 63%. The standard which is run has a concentration of 85g/dL, with an absorbance value of 4%.
What is the concentration of this unknown sample?
Concentration of unknown = (Absorbance of unknown ÷ Absorbance of standard) x Concentration of standard
Concentration of unknown = (63% / 85g/dL) x (4%)
Concentration of unknown = 2.96g/dL
Calculate the RCF of a centrifuge that has a radius of 50cm and is operated at 1000 rpms.
RCF = 1.118 x 10-5 x (r) x (rpm2)
RCF = 1.118 x 10-5 x (50cm) x (10002)
RCF = 559 x g
What is the variance and standard deviation of the following numbers:
5, 14, 17, 8, 12
(The mean is 11.2)
Standard deviation = sqrt((summation (Xn - mean)2)/n-1)
Variance = S2
standard deviation = sqrt((5-11.2)2 + (14-11.2)2 + (17-11.2)2 + (8-11.2)2 + (12-11.2)2)/(5-1)
standard deviation = 4.76
variance = 22.7