Question

1) A 10-milliliter graduate weighs 42.745 grams. When 6 milliliters of distilled water are measured in it, the combined weight of graduate and water is 48.465 grams. By definition, 6 milliliters of water should weigh 6 grams. Calculate the weight of the measured water and express any deviation from 6 grams as percentage of error (%, to the nearest hundredth)

2) A torsion balance has a sensitivity requirement (SR) of 7.5 mg. What is the MWQ of this balance if the maximum error permitted in using it is 7.2%? [round answer to a whole number]

Answer 1

data according to the question:

weight of 10 ml gradute - 42.745 gm

volume of water added - 6 ml

theoritical weight of water added - 6 gm

combined weight of graduate and water - 48.465 gm

a)

weight of the measured water = 48.465 - 42.745 gm = 5.72 gm

error in weight = (42.745 + 6) - 48.465 gm = 0.280 gm

percentage error in weight of water = (0.280/6)*100 % = 0.0467 % = 0.05 % (rounded off to nearest hudredth point)

b)

data given : SR = 7.5 mg

                    permitted error = 7.2 %

formula for Minimum weightable quantity (MWQ) = SR/permitted % error mg

                                                                             = 7.5/7.2%                   mg

                                                                             = 7.5/(7.2/100)            mg

                                                                              = 750/7.2                   mg

                                                                              = 104.167    mg

rounding the final to whole number. we get MWQ = 104 milligrams

hope the solution is clear and understandable.

Thank you.