Density Lab B

[azboy1910]

I edited my previous posts, so my new answers are there. I believe you are right for question 1, I divided by two thinking it was the diameter and not the radius, so sorry about that. For question 3, I switched T1 and T2 variables, so my answer was also wrong here, but I also saw when you added 40 K with the boiling point of water, you forgot to convert the water boiling point from Celsius to Kelvin. Sorry about this, I'm a little rusty and probably should get back to practicing these problems again, but thanks for showing how you got your answers.

[YellowMamba]

I guess I will go then.
1) A ball of an unknown material has a density of 16.3g/cm^3. It is placed in a bowl of water and the volume of the water goes up from 400mL to 800mL. What is the mass of the ball?
2) What is Gay Lussac’s Law? Provide an example question with an answer.
3) The pressure exerted by nitrogen in a sample of air is 926 mmHg. The pressure of oxygen exerted in the same sample is 252 mmHg. The pressure of the argon in the same sample is 542 mmHg. The pressure of all the other gases is 242 mmHg. In atmospheres, what is the pressure of the sample?
4) A 4 Liter sample of nitrogen is at standard temperature and pressure. (0˚ C and 1 atm). If the container then expands to 20 Liters, and the pressure is lowered to 0.86 atm, then what is the final temperature (Kelvins)?

[YellowMamba]

If nobody is going to answer by the 16th, I will answer them myself.

[azboy1910]

Sorry about that, I wanted to see if someone else was going to answer.

Click to Show Answer

Here are my answers. A few of them may be a little off b/c of the significant figures.

[YellowMamba]

Those are all correct! I was just a little confused when no one answered my questions after four days since usually it takes one or two days for an answer.

[azboy1910]

Ok, I guess I will go.

Use correct significant figures and metric units for the following questions.

1. Calculate the density in g/L of a spherical ball with a diameter of 4.00 cm and the same mass as 50.0 mL of ocean saltwater (about 1,025 g/L).
2. A tray with a height of 7.62 cm and a volume of 400.0 mL contains 95.5 miniature objects with the same volume. What is the areal number density of the objects in the tray in objects/m^2?
3. A rectangular prism pencil box with the dimensions 4.00 cm x 5.00 cm x 10.00 cm contains a gas that takes up the volume of the entire container. It is currently held at a pressure of 1.00 kPa and a temperature of 40.0 degrees Celsius. The temperature is increased by 20.0 degrees Kelvin. What is the new pressure of this gas?
4. Calculate the force exerted by a tennis ball with a mass of 56.5 g rested on a tennis court covering an area of 5 cm^2 with the dimensions 11.0 m x 24.0 m. What is the pressure exerted on the court by the tennis ball in atm?

[YellowMamba]

On #2 do the objects take up the entire tray?
On #4 I don’t think you can calculate the impact force without the height the tennis ball falls from.
On #4 To my understanding of pressure, we can’t figure out the pressure of the tennis ball on the court without knowing how much of the tennis ball touches the tennis court.

[azboy1910]

I fixed the problems that didn't make sense, please feel free to PM if you still see any errors. I'm sorry that I've made a mistake with my own problems again. Also, I'm not exactly sure what you mean for #2, because I'm not sure if it matters that they cover the whole tray.

EDIT: I fixed #4 again, sorry about that.

[YellowMamba]

Click to Show Answer

1. 1530 (3 sig figs)
2. (I’m not sure on this one) 0.0001819275
3. 1.0638715631
4. 0.0001094034

[azboy1910]

Click to Show Answer

1. 1530 (3 sig figs)
2. (I’m not sure on this one) 0.0001819275
3. 1.0638715631
4. 0.0001094034

Click to Show Answer

I agree with your answers for questions 1 and 3, just add the units (g/L for #1 and kPa for #3) and the appropriate number of significant figures for #3, 3 in this case, so round to 1.06, so the answer is 1.06 kPa. 

Units are also missing for #2 and 4, so just beware of that. I think that either you or I made a conversion error for either one or both questions 2 and 4. 

For number 2 (one sig fig from 5 square centimeter),


For number 4 (3 sig figs from multiple variables),



Please PM me in private if you still disagree with these answers