chem lab chapter 3

Convert 5.5 lb to kg

5.5lb * 454/1lb * 1kg/1000g

5.5 × 454kg/1000 = 2.5kg

final answer: 2.5kg

Convert 3.5kg/L to g/mL

3.5kg/L * 1000g/1klg * 1L/1000mL

Final answer: 3.5g/mL

Density of a substance

Density = mass/volume

specific gravity

specific gravity = density of a substance (g/mL) / density of water (g/mL)

(note: density of water is 1.00 g/mL)

1. A beaker has a mass of 77.275g

a. Calc this mass in mg

b. Calc this mass in lb

a. 77.275g * 1000mg/1g = 77,275mg (the grams cancel out')

b. 77.275/ 454 is approx., 0.1700 lb

2. The combined total mass in grams of a beaker and pure water is 95.175g

a. Find the weight of the water if the empty beaker weighs 54.795g ( subtraction)

b. Find the volume of the water has a density of 1.00g/mL? (d=m/v, then v=m/d)

a. 95.175 - 54.795 = 40. 300g

b. d=m/v, then make it v= m/d

v= 40.380g/ 1.00g/mL = 40.380mL

volume in L = 40.380mL * 1L/1000mL = 0.040380L

3. What is the total mass in grams of a series of samples that have masses of 753mg, 51.227g, and 0.437kg?

753mg * 1g/1000mg = 0.753g (the mg cancels)

0.437kg * 1000g/ 1kg = 437g (the kg cancels)

0.753g +437+51.227g = 488.98g

4. What is the density (g/mL) of a solid with a mass of 4.75g and a volume of 6.20mL?

d=m/v

d= 4.75g/ 6.20mL = 0.766g/mL

5. Find the mass (g) of a 257mL sample with a gravity of 1.75

Specific gravity = density of substance (g/mL) / density of water (g/mL)

1. Density = 1.75g/mL

2. Mass = density * volume’

Mass = 1.75g/mL * 257mL

3. 1.75 × 257 = 448.75g

4. 1.75 and 257 have 3 sig figs

Final answer: 450gg

6. How much time is required to administer 200mL of glucose IV solution if the flow rate is 5mL/min?

Total volume= 200mL

Flow rate = 5mL/min

Time= Volume/flow rate

Time=200mL/

_______ = 40 minutes

5mL/min

7. If the blood 10.5mg/dL of calcium and the human body normally contains 6 quarts of blood, what mass of calcium (in grams) will be found in the total blood volume?

calcium concentration: 10.5mg/dL

Total blood volume: 6 quarts

1. quarts —> liters —> deciliters

• 1 quart = 0.946L

6 ×0.846 = 5.676L

• 1 L = 10 dL

5.676L * 10 = 56.76dL

2. multiply concentration * total volume

10.5mg/dL * 56.76dL = 596mg

3. convert mg to grams

596mg * 1g/1000mg = 0.596g

Final Answer: about 0.60g

8. A patient needs 0.50 grams of a medication two times per day. How many 250mg tablets must the patient take per day?

1. g —> mg

0.50g * 1000mg/1g = 500mg (grams cancels out)

2. each tablet = 250mg

500mg/ 250mg/tablet = 2 tablets per dose

3. multiply by # of does per day

2 tablets / does * 2 doses/ day = 4 tablets/day