You are given 1.546 grams of a white powder and told that it is a mixture of potassium carbonate and sodium carbonate. you are also asked to determine the percent composition (percent sodium and potassium carbonate) by mass of the sample. to find the percent composition you decide to slowly add the powder to 10.00 ml of 1.15 m nitric acid until the bubbling stops. after adding the powder to the acid you reweigh your sample and its mass is 0.802 g. what is the percent composition by mass of the powder?