# chemistry

posted by cateye

you dissolve 6.55g of potassium nitrate in enough water to make a 250ml solution. if you add 1.25 l of additional water to this solution.what is the molarity of this new solution.

1. DrBob222

mols KNO3 = 6.55g/molar mass KNO3 = ?
M = mols/0.250L = ?M (old M)
New M = old M x [250 mL/(250+1250)] = new M IF (and only if) the volumes are additive; i.e., if 250 mL + 1250 mL actually makes EXACTLY 1,500 mL.

2. cateye

You have a 4.0 L steel tank containing hydrogen gas. You are able to heat or cool the tank and meaurse the pressure of the gas.

1.If the temperature is 25degree and the pressure is 3.5 aim ..How many grams of hydrogen does the tank contain.

2.at what temperatue in Celsius would you need a pressure of 5.5 atm?

3. DrBob222

Use PV = nRT and n = grams/molar mass.

4. cateye

I AM STILL CONFUSE..FOR THE FIRST I CAME OUT WITH .40 BUT FOR NUMBER 2 I STILL CAN FIGURE OUT THAT ONE..PLEASE HELP

5. DrBob222

I don't thik 0.40 is correct for #1. For #2, I'm not sure what it is asking?
#1.
n = PV/RT = 3.5*4/0.08206*298, then
grams = mols x molar mass. I get something like 1.1 or so. You need to do it a little more accuartely than that.

#2. Could be asking for "What T in celsius is needed to obtain a pressure of 5.5 atm?"
T(in kelvin) = PV/nR = 5.5*4/0.08206*0.572
Then 273+C = K and solve for C.

6. cateye

unbalanced chemical reaction equation:

CaCl2 (aq) + b Na3PO4 (aq)----> c Ca3 (PO4)2(s) + d NaCl (aq)
iF I start with 3.50 g calcium chloride (and sufficient sodium phosphate), what is my theoretical yield of calcium phosphate?

7. DrBob222

You would do well to post NEW questions as a new question and not tag it to one already answered. Why? Because we often check for new questions before we go back to the older ones; therefore, it COULD get overlooked.
Here is a worked example of how to calculate theoretical yield.
http://www.jiskha.com/science/chemistry/stoichiometry.html

8. cateye

I am try to follow the example but lost.. cant figure out how they got that 420

9. DrBob222

I don't see a 420 in anything.

## Similar Questions

1. ### science/chem

You dissolve 157.1 g of ammonium nitrate in a 250 mL volumetric flask and add water to the mark (call this solution A). You take 30 mL of solution A and place it in a 100 mL volumetric flask and add water to the mark (this is solution …
2. ### chemistry Molarity

You have 353 mL of a 1.25 M potassium Chloride solution, but you need to make a 0.50 M potassium Chloride solution. How many milliliters of water must you add to the original 1.25 M solution to make the 0.50 M potassium Chloride solution
3. ### Chemistry

If a 45.3-g sample of potassium nitrate is dissolved in enough water to make 225 mL of solution, what will be the molarity?
4. ### chemistry

you dissolve 0.70 moles of HCI in enough water to prepare 250ml of solution. what is the molarity of the solution you have prepared
5. ### Chemistry(Please Check)

You dissolve 6.55 g of potassium nitrate in enough water to make a 250. ML solution. 1.What is the molarity of this solution?
6. ### chemistry(Please Check)

You dissolve 6.55 g of potassium nitrate in enough water to make a 250. mL solution. What is the molarity of this solution ?
7. ### chemistry

What is the molarity (moles per liter) of an aqueous solution that is prepared by dissolving 5.58g NaOH (MW=40) in enough water to make 250mL of solution?
8. ### Chemistry

if you dissolve 25.5 g of KBr in enough water to make 1.75 L of solution, what is the molarity of the solution
9. ### Chemistry

A solution is prepared by dissolving 10.8 g of ammonium nitrate in enough water to make 100.0 mL of solution. A 10.0 mL portion of this sample is diluted to 50.0 mL total volume. What is the molarity of the final solution?
10. ### Chemistry

A solution is made by dissolving 55g of KCl in enough water to make 1.00 L of solution. Assume that the density of the solution is 1.00 g/mol. Calculate the mass percent, molarity, molality, and mole fraction of KCl.

More Similar Questions