Question

Saltpeter is a compound made of potassium (k), nitrogen (n), and oxygen (o). every 100.00 g of saltpeter contains 38.67 g potassium and 13.86 g nitrogen. what is the mass of oxygen contained in 328.0 mg of saltpeter

Answer 1

First, we need to compute the mass of oxygen found in 100 grams of saltpeter:
mass of oxygen = 100 - (mass of potassium + mass of nitrogen)
                          = 100 - (38.67 + 13.86)
                          = 100 - 52.53
mass of oxygen in 100 grams saltpeter = 47.47 grams

Now, we can use cross multiplication to find the mass of oxygen in 328 grams saltpeter as follows:
mass of oxygen = (328 x 47.47) / 100 = 155.7016 grams

Answer 2

Answer : The mass of oxygen contained is, 0.1557 gram

Solution : Given,

Mass of potassium = 38.67 g

Mass of nitrogen = 13.86 g

First we have to calculate the mass of oxygen contained.

Mass of oxygen contained = 100 - (Mass of potassium + Mass of nitrogen)

Mass of oxygen contained = 100 - (38.67 + 13.86) = 47.47 g

Now we have to calculate the mass of oxygen contained in 328.0 mg or 0.328 g.

(1 g = 1000 mg)

In 100 gram of water, the mass of oxygen contained = 47.47 g

In 0.328 gram of water, the mass of oxygen contained = $\frac{47.47}{100}\times 0.328=0.1557g$

Therefore, the mass of oxygen contained is, 0.1557 gram