Question

White gold is an alloy that typically contains 45.0% by mass gold and the remainder is platinum. if 154 g of gold are available, how many grams of platinum are required to combine with the gold to form this alloy?

Answer 1

Percent by mass of platinum in white gold = 100% - 45% = 55%

We let x be the mass of the white which is 45% gold and 55% platinum. 

Mass of gold in white gold = m x 0.45

where m is the total mass.

From the given above, we formulate the equation that would allow us to determine the mass of white gold.
                            154 = x (0.45)
                                     x = 342.22 g

Then, we determine the amount of platinum.
                     mass of platinum = (342.22 g)(0.55)
                      mass of platinum = 188.22 grams

Thus, 188.22 grams of platinum is needed.