1 - LAB - MATH-CHEM Answer KEY for scientific notation, metric system and chemistry review PDF

Preview

Summary

This is the Metric system, scientific notation and chemistry review answer key...

Description

Metric System, Scientific Notation, and Chemistry Review Answer key I. Scientific notation

Convert to standard notation:

Convert to scientific notation:

9.82 X 102 = 982

987,000 = 9.87 x 105

2.34 X 1010 = 23,400,000,000

0.567 = 5.67 x 10-1

5.67 x 103 = 5,670

8.75 = 8.75 x 100

5.2 X 10-3= 0.0052

8,750 = 8.75 x 103

2.54 X 10-5 = 0.0000254

0.000345 = 3.45 x 10-4

II. The metric system

1 m = 1000 mm

500 ml = 0.5 l

0.025 ml = 25 μl

0.450 l = 4.5 dl

10 cm = 0.1 m

1 dl = 0.1 l

0.0000000075 m = 7.5 nm

740 cc = 0.74 l

25 mm = 2.5 cm

33 kg = 33,000 gm

50 μsec = 0.05 msec

125 ml = 0.125 l

35 cm = 350 mm

1000 μl = 1 ml

35000 μm = 35 mm

325 μl = 0.325 ml

1 s = 109 nsec

100 cc = 100 ml

6500 m = 6.5km

30 cc = 0.3 dl

1

III.

Graphs and proportionality

Solve for the unknown variable: 1. 370 = 300 x 200

x = 246.67

2. _x_ = 1,200 3 35

x = 102.86

3. 3400 = 2300 200 x

x = 135.29

4. 123 =_ x_ 456 789

x = 212.82

Using the graph and information below, solve for the unknown variable:

2

1. x2 = 6.5; y2 = ?

y2 = 32.5

2. y2 = 65; x2 = ?

x2 = 13

3. x2 = 8.3; y2 = ?

y2 = 41.5

4. y2 = 45; x2 = ?

x2 = 9

3

1. At a paper speed of 25mm/sec, what is the distance that corresponds to 2 seconds of recording? x = 50mm 2. At a paper speed of 20mm/sec, what is the time interval that in encompassed by 13mm of recorded paper? x = 0.65sec 3. What is the paper speed of an output that received 1,020 linear millimeters of recorded tracings during 17 seconds? 60mm/sec 4. Given the tracing below, from a machine that produced output at a constant speed of 25mm/sec, calculate the duration, in seconds, of the event marked by the interval x x = 0.66 sec IV.

Solutions

1. How many grams of NaCl would you use to make 100ml of a 4M solution? 23.38g of NaCl 2. How many grams of glucose would you use to make 1L of a 2mM solution? (Note: mM = milimole = 1/1000 mole) 0.36g/1L 3. What is the molal and gm %concentration of a solution made of 20g of NaCl in a total volume of 100ml of water? 3.4 molal; 20gm% 4. How would you make 400ml of a 3% glucose solution? 12g 5. You weigh out 50g of MgCl2, 50g of CaCl2, and 50g of glucose in three separate cylinders and you add 100ml of water to each graduated cylinder. What are the gram percent concentrations for these solutions? 50gm% for all Why are they the same gm %? They all have the same mass per 100ml Calculate the molalities of these solutions. MgCl2 = 5.3 molal CaCl2 = 4.5. molal Glucose = 2.8 molal

4

Why aren’t the molalities the same? They have different MW and, hence, different number of moles per 50g

Calculate the osmolalities of these solutions. MgCl2 = 15.9-16 osm (answer depends on when a student rounded up in these questions) CaCl2 = 13.5 osm Glucose = 2.8 osm Why aren’t they the same? They have different molalities and different dissociation factors 6. What is the molal concentration of a 0.9% NaCl solution? 0.154 molal 7. What is the osmolar concentration of a 0.9% NaCl solution? 0.307 Osm (or 0.3 for sig fig) 8. What is the milliosmolar concentration of a 0.9% NaCl solution? 307mOsm (or 300mOsm for sig fig) 9. What is the g% concentration of a 180mM glucose solution? 3.24gm% 10. What is the g% concentration of a 180mM NaCl solution? 1.053gm% 11. What is the g% concentration of a 180mOsm glucose solution? 3.24 gm% 12. What is the g% concentration of a 180mOsm NaCl solution? 0.5265 gm%

V.

pH and log

Using the given concentrations of H+, calculate the pH using the formula pH = -log[H+]. Recall that this formula only works with concentrations given in Eq/L (or moles/L, which, in the case of H+, is a numerically equal form of representing concentration): 1. [H+] = 10-9.3 moles/L; pH = 9.3 +

-13.23

2. [H ] = 10

moles/L; pH = 13.23

3. [H+] = 0.000001 moles/L; pH = 6

4. [H+] = 0.00000302 moles/L; pH = 5.52 5. [H+] = 9.1 x 10-7 moles/L; pH = 6.04

5

6.

[H+] = 0.05µEq/L; pH = 7.3

6...