Question

How many grams of O2 are needed to react completely with 12.8 grams of K?
K + O2 ---> K20
Be sure to balance the equation.

Answer 1

A. 2.62 grams

B. 10.4 grams

C. 51.2 grams

D. 62.6 grams

Answer 2

can find mole of K? you are given mass and from periodic table you can see that molecular mass of K is 39.1

Answer 3

mole= mass / molecular mass
thus mole of K = 12.8 / 39.1 = calculate it

then the ratio between K and O2 in reaction is 1:1 thus mole of O2 will also be your calculated number
so use mole formula again but make mass as subject this time because you need O2's mass
mass= mole*molecular mass
so mass of O2 = your calculated mole * molecular mass of O2 which is (16*2)

Answer 4

Balanced equation: 2 K + O2 ---> K2O

Answer 5

ah yeah totally forgot the balancing part @Gebooors thanx for telling :)

Answer 6

please consider that the ration is 2:1 and do accordingly
im sorry i didn't see that mistake T_T