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### Topic: If 3.75 x 10^24 atoms of hydrogen...  (Read 510 times)

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#### kail.hoodi

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##### If 3.75 x 10^24 atoms of hydrogen...
« on: June 05, 2019, 08:28:10 PM »
Hi There,

Even though I did Chem 11 and got a good grade, I have to redo it as it has been over 10 years. I have some questions I am stuck on, and/or I am not sure if my answer is correct, I would like to double check before handing in this assignment.

9. If 3.75 x 10^24 atoms of hydrogen are found in a sample of ammonium chloride, what mass of ammonium chloride is present? NH4Cl molar mass - 53.50 g/mol

10. d.) How many molecules in 1.56 x 10^3 of methane gas at STP?

11. What volume at STP would....

a.) 6.85 x 10^22 molecules of sulphur dioxide take up.

b.) 68.7 g of helium take up.

c.) 1.78 mol of mercury gas take up.

d.) 7.51 x 10^25 molecules of nitrogen gas take up.

12.
a.) How much would 3.42 x 10^3 L of oxygen held at STP weigh?

b.) How many atoms of oxygen would be found in the above quantity of gas.

13. How much mass and volume (at STP) of gaseous tetraphosphorus hexaoxide would be present in 9.63 x 10^24 atoms of oxygen were found in the sample?

15. If the mass of lithium atom is 6.94 amu, and that of a uranium atom is 238.1 amu, calculate the mass of the lithium atom relative to that of the uranium atom.

THANK YOU!

#### Borek

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« Reply #1 on: June 06, 2019, 02:51:50 AM »
You have to show your attempts at answering the problems to receive help, this is a forum policy.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

#### kail.hoodi

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##### If 3.75 x 10^24 atoms of hydrogen...
« Reply #2 on: June 11, 2019, 10:35:16 PM »
If 3.75 x 10^24 atoms of hydrogen are found in a sample of ammonium chloride, what mass of ammonium chloride is present? NH4Cl Molar Mass = 53.50 g/mol

Please let me know if I am right.

3.75x10^24/53.50 = 7.009346x10^23

Thank you

#### kail.hoodi

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##### How many molecules?
« Reply #3 on: June 11, 2019, 10:39:19 PM »
How many molecules in 1.53 x !0 ^3L of methane gas at STP?

1.56x10^3L/22.4L x 100 = 6964.86%

6964.86 x 6.022x 10^23

= 4.1939x 10^29 mol

#### kail.hoodi

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##### What volume at stp would?
« Reply #4 on: June 11, 2019, 10:46:13 PM »
What volume at STP would?

a) 6.85 x 10^22 molecules of sulphur dioxide take up?

6.85 x 10^22 / 22.4 L = 3.06x10^22

3.06 x 10^22 x 22.4

= 6.85x 10^23 mol/L

b)68.7 g of helium take up?

68.7 g / 4.00 g/mol, = 17.175 mol

v= nRT/P = 17.175mol x 0.08206 x 273.15 / 1 atm

= 384.97

c) 1.78 mol of mercury gas take up?

1.78 mol x 22.4 L

= 39.9L

d) 7.51 x 10 ^25 molecules of nitrogen gas take up?

7.51 x 10^22 mol x 22.4 L

= 1.68 x 10^27 L

#### kail.hoodi

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##### Re: What volume at stp would?
« Reply #5 on: June 11, 2019, 10:46:52 PM »
Please let me know if I am correct or not!

#### kail.hoodi

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« Reply #6 on: June 11, 2019, 11:46:56 PM »
Thank you so much. I will do this right away!

#### kail.hoodi

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« Reply #7 on: June 11, 2019, 11:49:57 PM »
How much would 3.42 x 10^3L of oxygen (held at stp) weigh?

2.42 x 10 ^3 / 2.205

= 1551

How many atoms of oxygen would be found in the above quantity of gas?

#### Borek

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##### Re: If 3.75 x 10^24 atoms of hydrogen...
« Reply #8 on: June 12, 2019, 03:19:06 AM »
I have combined all your posts in a one thread, as they are all very similar and you are making all the time the same mistakes.

First of all: units. You consistently fail to name units in which your answer is given:

How much would 3.42 x 10^3L of oxygen (held at stp) weigh?

2.42 x 10 ^3 / 2.205 = 1551

1551 of what? Stones? Pounds? Grams?

Second, in most cases it looks like you are randomly using some numbers to divide or multiply, in a hope it will produce a correct result:

How many molecules in 1.53 x !0 ^3L of methane gas at STP?

1.56x10^3L/22.4L x 100 = 6964.86%

You don't need percentage here. Plus, what you have really calculated is not a percentage, it is even difficult to say what it is