Question

How many grams of KClO3 are needed to produce of 4.26 moles of O2? 2 KClO3 2 KCl + 3 O2 a. 348 g b. 136 g c. 174 g d. 522 g e. 783 g

Answer 1

Ok so this is what we know :

2KClO3 -> 2KCl + 3O2         (Always check if equation is balanced - in this                                               case it is)
                              4.26moles
So we know that we have 4.26 moles of oxygen (O2). Now lets look at the ratio between KClO3 and O2.
We see that the ratio is 2:3 meaning that we need 2KClO3 in order to produce 3O2.
Therefore divide 4.26 by 3 and then multiply by 2.
4.26/3 = 1.42
1.42 * 2 = 2.84
Now we know that the molarity of KClO3 is 2.84 moles.
Multiply by R.M.M to find how many grams of KClO3 we have.

R.M.M of KClO3
K- 39
Cl- 35.5
3O- 3 * 16 -> 48
---------------------------
                      122.5
2.84 * 122.5 = 347.9 grams therefore the answer is (a)
                       348 grams needed of KClO3 to produce 4.26 moles of O2.
Hope this helps :).

Answer 2

Answer:

The answer is c. 173 g

Explanation:

You know the reaction :

KClO3 ⇒ 2 KCl + 3 O2

By stoichiometry, that is, the amount of reagents and products in a chemical reaction when it is balanced (as in this case), it is known that for 2 moles of O2, 1 mole of KCLO3 is needed. So you can do the following rule of three to know the number of moles to produce 4.26 moles of 02:

If 1 mole of KClO3 is necessary to produce 3 moles of O2, how many moles are needed to produce 4.26 moles of 02?

$\frac{4.26moles 02*1 mol KClO3}{3 moles O2} = 1.42$

So you need 1.42 moles of KClO3

Now it is necessary to know the molar mass of KClO3, which is the mass that contains 1 mole of the substance. For that you need to know the mass of K, Cl and O:

• K: 39 g/mol
• Cl: 35.45 g/mol
• O:  16 g/mol

So, the molar mass of KClO3 is:

39 g/mol + 35.45 g/mol + 3*16 g/mol=122.45 g/mol

because it contains 1 atom of K, 1 atom of Cl and 3 atoms of O.

Now, to calculate the mass representing 1.42 moles of KClO3 (needed to produce 4.26 moles of O2) you simply multiply that amount of moles by the molar mass:

$1.42moles*122.45\frac{g}{mol} =173.88 g$

This means that approximately 174 g of KClO3 are necessary to produce 4.26 moles of O2.