August 2009 Chemistry Regents #77-79

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Base your answers to questions 77 through 79 on the information below.

 

A method used by ancient Egyptians to obtain copper metal from copper(I) sulfide ore was heating the ore in the presence of air. Later, copper was mixed with tin to produce a useful alloy called bronze.

77 Calculate the density of a 129.5-gram sample of bronze that has a volume of 14.8 cubic centimeters. Your response must include a correct numerical setup and the calculated result. [2]

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d=m/v   d=129.5g/14.8cm3= 8.75g/cm3

78 Convert the melting point of the metal obtained from copper(I) sulfide ore to degrees Celsius. [1]

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1084C

C=1357K-273

 (melting point of copper Table S) 

79 A 133.8-gram sample of bronze was 10.3% tin by mass. Determine the total mass of tin in the sample. [1]

HIGHLIGHT TO SEE THE ANSWER

  Mass=13.8g

(133.8g x 0.103)

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