Ma 3- Law of Definite Proportions

Front

What is the Law of Definite Proportions?

Back

The Law of Definite Proportions states that a chemical compound always contains its component elements in fixed ratio by mass, regardless of the amount of the compound.

Front

How do you calculate the percent by mass of an element in a compound?

Back

Percent by mass = (mass of the element / total mass of the compound) x 100%.

Front

If a compound has a total mass of 105g and contains 54g of element Q, what is the percent by mass of element Q?

Back

51%.

Front

In a decomposition reaction, if 55g of CuO produces 44g of Cu, what is the mass of oxygen that escaped?

Back

11g (55g - 44g).

Front

What is the percent by mass of oxygen in CuO if 11g of oxygen is lost from 55g of CuO?

Back

20%.

Front

If 43g of element X combines with 4.2g of element Y and 5.6g of element Z, what is the total mass of the compound XYZ?

Back

52.8g (43g + 4.2g + 5.6g).

Front

What is the percent by mass of element X in the compound XYZ?

Back

81%.

Front

What is the percent by mass of element Y in the compound XYZ?

Back

8%.

Front

What is the percent by mass of element Z in the compound XYZ?

Back

11%.

Front

If a compound contains 30g of element A and 70g of element B, what is the percent by mass of element A?

Back

30%.