Question

Determine the boiling point of water at 620 nun Hg

A pipet delivers 9.98 g of water at 20°C. What volume does the pipet deliver?

A pipet delivers 10.4, 10.2, 10.8, and 10.6 mL in consecutive trials. Find the mean volume and the average deviation from the mean.

A 141-mg sample was placed on a watch glass that weighed 9.203 g. What is the weight of the watch glass and sample in grams?

(a) Using the defined freezing and boiling points of water, make a plot of degrees Fahrenheit versus degrees Celsius on the graph paper provided. (b) Determine the Celsius equivalent of 40°F using your graph. The relationship between these two temperature scales is linear (i.e., it is of the form y = mx + b). Consult Appendix B regarding linear relationships and determine the equation that relates degrees Fahrenheit to degrees Celsius. (c) Compute the Celsius equivalent of 40°F using this relationship

. A man who is 5 ft 8 in. tall weighs 160 lb. What is his height in centimeters and his mass in kilograms?

Drug medications are often prescribed on the basis of body weight. The adult dosage of Elixophyllin, a drug used to treat asthma, is 6 mg/kg of body mass. Calculate the dose in milligrams for a 150-lb person.

Carry out the following operations, and express the answer with the appropriate number of significant figures and units. (a) (5.231 nun)(6.1 nun); (b) 72.3 g/1.5 mL; (c) 12.21 g + 0.0132 g; (d) 31.03 g + 12 mg.

Answer 1

1. As boiling of the liquid is the temperature when the vapour pressure of the liquid become equal to the atmospheric pressure.

Pressure (P) = 620 mmHg

As we know the atmospheric pressure is 760 mmHg

So, substract atomspheric (atm) pressure to the current pressure given in the question. we will get

As the current pressure is lower than that of atm pressure. Temperature is lower than that of boiling point at the 760 mmHg which is 100^o C.

decrease in pressure = 140 mmHg

Every 28 mmHg decrease in the pressure results in decreses approx. 1^o C boiling point.

So, we have to divide this number with decrease in pressure

decrease in temperature = 140/28 = 5^o C

boiling point of water at 620 mmHg = 100^o C - 5^o C = 95^o C

2. As we know the density of water at 20^o C is 0.998 g/ml

So, density= mass/volume

volume = 9.98/0.998 = 10 ml

Volume of pipet deliver is 10 ml

3. mean volume = sum of all the volume / no. of volumes

= (10.4+10.2+10.8+10.6)/4 = 10.5 ml

Average deviation = (sum of all the difference between the measure volume and mean volume)/ no. of volume

= [|(10.4-10.5)|+|(10.2-10.5)|+|(10.8+10.5)|+|(10.6-10.5)|]/4

Note all the difference has mode.

= (0.1+0.3+0.3+0.1)/4 = 0.2 ml

4. Weight of sample = 141 mg = 141x 10^-3 g =0.141 g

Weight of watchglass and sample = 9.203 g

Weight of watchglass = Weight of watchglass and sample - Weight of sample

= 9.203 g - 0.141 g = 9.062 g

5. Boiling point is the temperature when the vapour pressure of the liquid become equal to the atmospheric pressure. Boiling point of water is 100^o C.

Freezing point is the temperature at which the liquid start solidifing. Freezing point of water is 0^o C.

The relation between the degrees Fahrenheit (F) and degrees Celsius (C)

F = (9/5) C + 32 .....(1)

Using the straight line equation you can plot the graph.

y = mx + c

y = F, m= slope = (9/5), x = C, c= intercept = 32

6. Put the value of temp in F to equation (1)

40 = (9/5) C +32

C = (8 * 5)/9 = 40/9 = 4.44^o C

7. Height = 5 ft 8 in

1 ft = 30.48 cm

1 in = 2.54 cm

Putting this value in given height, we will get height in cm

Height = 5*30.48 + 8*2.54 = 152.4 + 20.32 = 172.72 cm

8. Weight = 160 lb

1 lb =0.454 kg ....(2)

Putthing this in weight convert to kg

Weight = 160*0.454 = 72.64 kg

9. dosage body by weight ratio = 6 mg/kg

1 kg person requires = 6 mg dosage

0.454 kg person requires = 6*0.454 mg dosage =2.724 mg dosage

1 lb person requires = 2.724 mg dosage

150 lb person requires = 150 * 2.724 mg dosage = 408.6 mg dosage

10. Rules of significant figure in multiplication/division/addition/subtraction

We have to catagorise our rules in two.

(1) multiplication/division = Round off the value to the least number of significant figure.

(2) addition/subtraction = Round off the value to the least number of decimal place.

(a) (5.231 nun)(6.1 nun) = 32 nun² (least no. of significant figure is two, so round of 31.9091 to 32.)

(b) 72.3 g/1.5 mL = 48 g/mL (least no. of significant figure is two, so round of 48.2 to 48.)

(c) 12.21 g + 0.0132 g = 12.22 g (least no. of decimal figure is two, so round of 12.2232 to 12.22.)

(d) 31.03 g + 12 mg = 31.03 g + 0.012 g =31.042 g (least no. of decimal figure is zero, so round of 31.042 to 31.)