Brass is an alloy of copper and zinc. varying the mass per- centages of the two metals produces brasses with different proper- ties. a brass called yellow zinc has high ductility and strength and is 34–37% zinc by mass. (a) find the mass range (in g) of copper in 185 g of yellow zinc. (b) what is the mass range (in g) of zinc in a sample of yellow zinc that contains 46.5 g of copper?

First step: The mass of zinc in the yellow zinc sample can be calculated with the help of percentage (given) in the sample. After that, mass of copper is determine by the subtracting the mass of zinc from the total mass of zinc in the given sample.

Thus,

Mass of zinc in 34% zinc sample =

= zinc

Mass of zinc in 37% zinc sample =

= zinc

Now,

mass of copper in 34% zinc sample =

=

mass of copper in 37% zinc sample =

=

Thus, the range of mass of copper is to  

Second step:

34% zinc sample consist of 66% copper (100-34= 66%)

37% zinc sample consist of 63% copper (100-37=63%)

Mass of zinc =

=

Mass of zinc  =

=

Thus, the range of mass of zinc is to  

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.