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Chemistry 101

Measurements in Chemistry

Laboratory 3

Name ______Section ______

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In most scientific work, we frequently need to convert a measurement from one unit to another. There are many ways to accomplish these conversions: (1) factor-label-method; (2) dimensional analysis; and (3) unit conversion method. In all these methods, we follow the rule that when multiplying numbers we also multiply units, and when dividing numbers we also divide units. Conversions factors are also useful for calculating medications. For example, if an antibiotic is available in 5-mg tablets. The dosage can be written as a conversion factor, 5 mg/1 tablet.

For conversions between one unit and another, it is always possible to set up two fractions, called conversion factors. For example, suppose we wish to convert 381 g to pounds. We will look for the relationship between grams and pounds. There are 453.6 g in 1.0 lb. The conversion factors between grams and pounds, therefore, are:

1. 1.0 lb and 2. 435.6 g

453.6 g 1.0 lb

For example, to convert 381 g to pounds, we need to use conversion factor (1).

381 g x 1.0 lb = 0.840 1b

453.6 g

PROBLEMS:

  1. The distance between Rome and Milan (two largest cities in Italy) is 358 miles. How many kilometers is this?
  1. The maximum speed limit on many roads in the United States is 65 miles per hour(65 mph). How many meters per second is this (m/s)?
  1. (a). The recommended dose of a medication is 5.0 mg/kg body weight. You have a patient whose weight is 125 lb. The pharmacy offers the medication in three different pills containing (a) 500 mg, (b) 250 mg, and (c) 100 mg. Which pill will you administer to the patient? ( Show your work).

(b). If the recommended dose of a drug is 445 mg for a 180-lb man, what would be suitable for a 135-lb man?

(c) The average lethal dose of heroin is 150 mg/kg of body weight. Estimate how many grams of heroin would be lethal for a 200-lb man. (Show your work).

  1. How many milliliters are in 2.35 gallons?
  1. How long would it take to drive 375 miles at 55 miles per hour? Calculate your answer in:

(a). hours

(b) seconds

  1. A prescription for nifedipine calls for 0.2 mg/kg of body weight, four times per day. The drug is packaged in capsules of 5 mg. How many capsules per dose should be given to a patient who weighs 75 kg? ( Show your work)
  1. A patient needs 0.024 g of a sulfa drug. There are 8.0-mg tablets in stock. How many tablets should be given to the patient? (Show your work).
  1. A physician has ordered 325 mg of atropine, intramuscularly. If atropine were available as 0.5og/mL of solution, how many milliliters would you need to give? (Show your work).
  1. A dialysis unit requires 75,000 mL of distilled water. How many gallons of distilled water are needed? (1 gal = 4qt).
  1. Amy’s diet restricts her intake of protein to 24 g per day. If she eats 1.2 oz of protein, has shed exceeded her protein intake for the day? (Show your work).
  1. The recommended daily dose of calcium for an 18-year old male is 1200 mg/day. If 1.0 cup of whole milk contains 290 mg of calcium and milk is the only calcium source, how much milk should an 18-year male drink each day? (Show your work).
  1. The normal value for blood cholesterol is 200 mg/dL. If a normal adult has a total blood volume of 5 L, how much total cholesterol is present?
  1. A patient is receiving 3000 mL/day of a solution that contains 5 g of dextrose(glucose) per 100 mL of solution. If glucose provides 4.0 kcal/g of energy, how many kilocalories per day is the patient receiving from the glucose? (Show your work).
  1. How many grams are there in 1 oz? ( Hint: there are 16 oz/lb)
  1. How many milligrams are there in 1 oz?
  1. Perform the following conversions:

(a)Convert 75 oF to Celsius degrees.

(b)Convert 125 oC to Fahrenheit degrees.

(c)Express 37 oC in kelvins

17. How many joules are necessary to raise the temperature of 1.500 kg of a substance whose specific heat is 0.850, from 25 oC to 75 oC? (Hint: Heat = Cp x mass of sample x ∆t ).

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