Question

_ g of potassium reacts with 16 g of oxygen to produce 94 g of potassium oxide

Answer 1

Due to the law of conservation of mass, _g K + 16g O=94g KO.
So, 94-16=78
78 is your answer

Answer 2

Answer:

78 g of potassium

Explanation:

According to Lavoisier's Law, the sum of the mass of the products must be equal to the sum of the mass of the reactants.

On the reaction we have potassium oxide as product (K2O) and as reactants potassium (K) and Oxygen (O2)

Having sayin this, the reaction must be as follows:

K + O2 -> K2O

We need to balance the equation  to have the same amount of molecules of each element in each side:

4K + O2 -> 2K2O

Taking into account the  molar mass of each compound, the reaction can also be written:

4(39g/mol) + 1(32g/mol) -> 2(94g/mol)

solving the  multiplications we have that:

156g of K + 32g of O2 -> 188g of K2O

therefore, we need 78 g of K to obtain 94 g of K2O with 16g of O2