If 1.123 g strip of Cu is used for the reaction? How many moles of Cu were react

Question

If 1.123 g strip of Cu is used for the reaction? How many moles of Cu were reacted (Remember to use correct significant figures and show your work) After the reaction, the strip now weighs 1.345 g. How much mass was gained This gain in weight is attributed to that mass of what element? Using the information from above, how many moles of sulfur were reacted? (Remember to use correct significant figures and show your work) What is the difference between an endothermic reaction and an exothermic reaction?

Explanation / Answer

(1) Number of moles of Cu , n = mass/molar mass

= 1.123 g / (63.5 g/mol)

= 0.0180 moles

(2) The amount of mass gained = final mass - initial mass

= 1.345 - 1.123 g

= 0.222 g

The added element was sulphur

(3) The number of moles of sulphur reacted , n = mass / molar mass

= 0.222 g / ( 32 g/mol)

= 6.940x10-3 moles

(4) Endothermic reaction is the one where energy/heat is absorbed by the system

where as in exothermic reaction heat energy will be released by the system

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