can someone help me please!?

Question

Can someone explain to me how to do Straight-weight Problems! I am doing chemistry and I can not figure it out. I just want someone to please break it down for me in a way I can understand it.... Thank you! I'll give you an example of the type of problems I am doing, but I am not asking for the answer just how to figure them out. Thank you!

How many grams of mercuric oxide are needed to produce 96 grams of oxygen?

How many liters of oxygen may be obtained by electrolysis of 900 grams of water?

What volume of sulfur dioxide is produced when 224 grams of sulfur are burned?

What weight of sulfuric acid must react with copper in order to produce 112 liters of sulfur dioxide? 490g

Thanks again!

okay, thank you for the help, but what i can not figure out also is how to make it into an equation?

How many grams of zinc chloride are produced when 3255 grams of zinc react with hydrochloric acid?

okay i know zinc chloride is ZnCl2 and hydrocloric acid is HCl but how do you place it together in an equation?

Answer 1

The method is very simple. I can do the first and you can try the others.

1. First write the reaction and balance it.

2HgO ---> 2Hg + O2.

2. Convert grams to moles of whatever mass you have. In this case you have O2 as 96 grams. You convert to moles by dividing the mass by the molecular weight. In this case, for O2 will be 32 g/mol

96 grams / 32 g/mol = 3 mol.

3. Now you look back to the equation. In the equation for producing 1 mol O2 you need 2 moles of HgO. If now have 3 moles O2, then you will need 2 x 3 moles of HgO, 6 moles.

4. Now you need to convert the moles of HgO to grams. To do this calculate the molecular weight of HgO. It is 216.6 g/mol

6 moles * 216.6 g/mol = 1299.6 g of HgO.

Answer 2

General method of thinking:

1. Make sure you have the balanced equation - you will need the coefficients later.

2. Identify what you have been GIVEN (the substance you have a quantity for;)I'll refer to this as substance A. In your first example it would be 96 grams of oxygen; in the second example it would be 900 grams of water; in the third example it would be 224g of sulfur; in the fourth example it would be 112 liters of sulfur dioxide.

2. Identify what quantity and what substance you are trying to find the answer for (this is the "what or "how much" question). I will refer to this substance as "B". In your first example it is "grams of mercuric oxide"; in your second example it is "liters of oxygen"; in your third example it is "vol. sulfur dioxide"; in the fourth example it is "weight of sulfuric acid".

3. Change the given quantity of substance "A" to MOLES of A.
a. If you have grams, divide by the molecular mass of "A".
b. If you have liters of a GAS, divide by 22.4 liters (all of your examples are gases) ALL gases occupy 22.4 liters per mole so it doesn't matter what the gas is.

4. Look at the balanced equation; find the coefficient in front of substance "A; and the coefficient in front of substance "B". Use this ratio to change "moles of A" ( your answer above) to moles of "B" Use ratio and proportion or dimensional analysis to do this.

5. You now have moles of "B" - change these to whatever you are asked for.
a. If you were asked for grams or weight of "B" multiply by the molecular mass of "B".
b. If you were asked for liters or volume of "B" and "B" is a gas, multiply by 22.4. In all of your examples, "B" is a gas.





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