# Posts by Hannah

Total # Posts: 3,341

**Chemistry**

For the reaction Al(s) + 3 HCl(aq)->AlCl3(s) +3/2 H2(g) it was observed that when 4.00g of aluminum reacted with excess HCl, exactly 30,0 kJ of heat was released. What is the delta H for this reaction? I do not understand how to get the delta H value.

**Chemistry**

Ok I got 54.9 which would round to 55 which is an answer choice that they gave me.

**Chemistry**

I am having trouble with getting Tf by itself that's all.

**Chemistry**

A cup of teat containing 400g of liquid at 20 degrees celsius was heated. If 58.5 kj of heat was absorbed by the tea, what would the final temperature be? Assume that the specific heat of the tea is the same as that of water (4.18). I am not sure how to start this problem. ...

**Physics**

You have 2 photos of a bicyclist. One shows the rider at the corner of Third and Main streets, the other shows the rider at Twentieth and Main. There are lampposts at every corner in this town, and the first picture shows it to be 10:32:00 exactly. The second picture shows it ...

**Chemistry**

O ok I thought that b was correct also but I see now why it is not.

**Chemistry**

2)Which of the following equations represents a reaction for which the delta H can be called a standard enthalpy of formation, delta Hf? a) FeO(s) + CO2(g) -> FeCO3(s) b) 1/2 N2(g) + 2 O(g) -> NO2(g) c) 2 Na(s) + Cl2(g) -> 2 NaCl(s) d) Ba(s) + N2(g) + 3 O2(g) -> Ba...

**Chemistry**

I did 400/58.5 (4.18) and got 28.6 degrees celsius. Was I suppose to use the 20 degrees that was stated in the problem?

**Chemistry**

so I did 4.18 = 400 X 58.5 X (Tf-30) 4.18 =I amnot sure what to do on this side. Do I multiply 400, 58.5 and 30?

**Chemistry**

A cup of teat containing 400g of liquid at 20 degrees celsius was heated. If 58.5 kj of heat was absorbed by the tea, what would the final temperature be? Assume that the specific heat of the tea is the same as that of water (4.18). I am not sure how to start this problem.

**Chemistry**

Yes all the units are kJ.

**Chemistry**

Did I do this correctly?

**Chemistry**

1) Consider the formation of sulfur trioxide according to the reaction: 2 SO2(g) + O2(g) -> 2 SO3(g) delta H = -198 How much heat is evolved in the formation of 750 grams of SO3? So I did 193 X (750/2*80.0642) = 904. The answer choices given are 10.6, 928, 1.86 X 10^3, 7.43...

**Chemistry**

So I did 193 X (750/2*80.0642) = 904. The answer choices given are 10.6, 928, 1.86 X 10^3, 7.43 X 10^4, 3.71 X 10^3 And how did you get 193?

**Chemistry**

1) Consider the formation of sulfur trioxide according to the reaction: 2 SO2(g) + O2(g) -> 2 SO3(g) delta H = -198 How much heat is evolved in the formation of 750 grams of SO3? I am not sure how to start this problem.

**Chemistry(Please check)**

Ok for number one i got 0.129 and for number 2 did you mean that my answer choice of e was correct or that just equation d is correct? Thank you for your help!!

**Chemistry(Please check)**

1)A piece of metal with a mass of 5.50 grams changed in temperature from 25 to 55 degrees celsius when 21.3 joules was absorbed. What is the specific heat of the metal? a)0.256 b)0.129 c)3.91 d) 7.75 e)0.710 Jg^-1 C^-1 I chose 7.75 because I did 5.50/21.3 and then multiplied ...

**Chemistry**

The four statements below are used for applications of Hess's law. One of the statements is erroneous. Choose that statement. a) the value of delta H for any reaction that can be written in steps is the sum of the values of delta H for each of the individual steps. b) when...

**chemistry(Please check)**

Thank you for checking my work!!!

**chemistry(Please check)**

1)Which thermochemical equation and data does not agree with the other two written? a) 2NO (g)+ O2 (g) ->2 NO2 (g) deltaH=-169.8 b) NO (g) + 1/2 O2 (g) -> NO2 (g) delta H = -56.6 c) 4 NO2 (g) -> 4 NO (g) + 2 O2 (g) delta H = +226.4 d)all three equations are in ...

**Chemistry**

ok so the lowest mass is Xe and the highest mass is NO2.

**Chemistry**

Is K the temp in kelvins? So for an example He would be 373K(sqrt 1/4.0026) = 186.43 Did I do that right?

**Chemistry**

Which molecule below has the greatest average velocity at 100 degrees celsius? He, Cl2, Xe, O2, NO2 I know that I already posted this the other day and the response I was given was to use the root mean squared equation. I know that the molecule with the smallest mm will be the...

**chemistry**

What is the molarity if 750. mL of a solution containing 332.5g of copper (II) sulfate

**Chemistry**

Ok thank you

**Chemistry**

Exactly 5.02 grams of an unknown gas was sealed in a 3.0L flask at 37 degrees celsius and a pressure of 1.25 atm. Which on of the following is most likely to be the unknown? H2O, HBr, HCN, H2S, C2H2 ok so I did (1.25)(3.0) = n(0.0821)(310) 3.75 = n(25.451) n=0.1473 Then I did ...

**Chemistry**

ok so I did (1.25)(3.0) = n(0.0821)(310) 3.75 = n(25.451) n=0.1473 Then I did 0.1473= 5.02/mm but I am not sure if this is right.

**Chemistry**

Exactly 5.02 grams of an unknown gas was sealed in a 3.0L flask at 37 degrees celsius and a pressure of 1.25 atm. Which on of the following is most likely to be the unknown? I am not sure how to start this.

**Chemistry**

oh ok because the answer of 0.258 threw me off but I understand why that's not the answer.

**Chemistry**

Ok so the answer has to be in mm Hg since the total pressure was in mm Hg correct?

**Chemistry**

Nevermind I didn't realize 1380 was stated in the problem, but I still not sure which answer choice to choose.

**Chemistry**

Ok and how did you get 1380? When I did 0.258*1380 I got 356.04. The answer choices that they gave me are 0.258atm, 300mm Hg, 360 mm Hg, 5300mm Hg, and 8000 mm Hg.

**Chemistry**

ok so for Ar i got 1.49. Then I added 1.27+1.49+3.04 = 5.8 and then I did 1.49 / 5.8 = 0.256. Now do I have to multiply 0.256 by the total?

**Chemistry**

A mixture of three gases has a total pressure of 1380 mm Hg at 25 degrees celsius. If the mixture contained 56 grams CO2, 3.04 mol CO and 9.03 X 10^23 atoms of Argon, the partial pressure of argon would be about? ok so first I did 56 CO2 X 1/44.01 = 1.27 then 3.04 CO X 1/28....

**Chemistry**

Ok I understand thank you!

**Chemistry**

I got 467460 = p2(683.85) then i divided 683.85 by 467460 and got 683.57. Th answer choices that were given are 110 mm Hg, 680mm Hg, 260 mm Hg, 280 mm Hg, and 1560 mm Hg so the closest to my answer is 680. Does that sound correct?

**Chemistry**

A sample of chlorine gas at a pressure of 420 mm Hg and in a volume of 3.50L was heated from 18.0 degrees celsius to 45 degrees celsius after being transferred to a container of volume 2.35L. The pressure in this new container should be about? The original T is 18 degrees ...

**Chemistry**

Ok thank you!!

**Chemistry**

Maybe, so in that case I would just have to plug everything into the van der waals equation to find the answer?

**Chemistry**

My teacher is going to list the molar masses of five gases and ask us which has the largest molar volume at STP. How would I go about solving this? Would the smallest number have the largest volume?

**Chemistry**

ok so first I did 56 CO2 X 1/44.01 = 1.27 then 3.04 CO X 1/28.01 = 0.108 then 9.03e23 Ar X 1/39.95 = 2.26e22 but im not sure I did this right. Is this correct so far before I continue? Thank you for your help.

**Chemistry**

A mixture of three gases has a total pressure of 1380 mm Hg at 25 degrees celsius. If the mixture contained 56 grams CO2, 3.04 mol CO and 9.03 X 10^23 atoms of Argon, the partial pressure of argon would be about? First I did 9.03e23 * 760/1 = 2.26e22 and then I was going to do...

**Chemistry**

According to the ideal gas law a 9.03 sample of oxygen gas in a 0.8112 container at 499k should exert a pressure of 456atm. By what % does the pressure calculated using van der waals equation differ from the ideal pressure? For O2 gas a=1.36 L^2atm/mol2 and b=3.18e-2 Hint: %...

**chemistry**

My teacher is going to list the molar masses of five gases and ask us which has the largest molar volume at STP. How would I go about solving this?

**Chemistry**

Yes the original T is 18 degrees celsius so would it be 420*3.50 / 291 K = p2 * 2.35 / 318 5.05 = p2 * 2.35 / 318. I am just not sure how to solve for the right side of the equation to find p2.

**Chemistry**

A sample of chlorine gas at a pressure of 420 mm Hg and in a volume of 3.50L was heated from 18.0 degrees celsius to 45 degrees celsius after being transferred to a container of volume 2.35L. The pressure in this new container should be about? Would I use (p1)(v1) = (p2)(v2) ...

**Chemistry**

so I just have to compare the molar mass of each gas and the smallest is the greatest?

**Chemistry**

What is RT? So for He I would do square root 3 times (value of RT) / 1.0079 correct?

**Chemistry**

Which molecule has the greatest average velocity at 100 degrees celsius. He, Cl2, Xe, O2, NO2 I used the root mean squared formula but I think I did it wrong. I got Xe as my answer. Is this correct?

**Chemistry**

ok thank you

**Chemistry**

Well the answer choices were 18L, 8.0L, 12.8L, 15L and 11.3L and when i divided 12 by 0.9399 which I got from 313/333 I got 12.76.

**Chemistry**

I tried again and got 12.8

**Chemistry**

I got 11.3 L as my answer. Is this correct?

**Chemistry**

So would I set it up as 12.0L / v2 = 313 K / 333K ?

**Chemistry**

A 12.0L sample of a as at a constant pressure of 608 mm Hg was heated from 40 degrees celsius to 60 degrees celsius. What volume does the gas now occupy? would I multiply 608 by 12 and then divide by the degrees celsius?

**Chemistry**

O ok thank you!!

**Chemistry**

What compound forms when one molecule of HCl and one molecule of NH3 combine? It is an ionic compound. I am not sure how to find this out. I thought is was H3O but that is not right.

**Chemistry**

Which molecule below has the greatest average velocity at 100 degrees celsius? He, Cl2, Xe, O2, NO2 I am not sure how to find this out. Thank you for your help!

**Statistics**

Long form: start with: 0.15 / (square root of n) = 0.01 multiply both sides by (square root of n) which gives you: 0.15 = (0.01) x (square root of n) divide both sides by 0.01 which gives you: 0.15 / 0.01 = square root of n both sides to the power of 2: (0.15 / 0.01)^2 = (...

**Chemistry**

I got 2.98g/L. Is this correct?

**Chemistry**

Calculate the density of sulfur trioxide gas at 35 degrees celsius and 715 torr pressure. I know that d=m/v = PM/RT. Im not sure how to set this up. I know the molar mass of sulfur trioxide is 80.0642 but im not sure if I need to use that.

**Chemistry(Please check)**

1) Which statement below is incorrect if any? a)when gas is at STP, the pressure of the gas is at 1.00 atm. b)when a gas is at STP, the temperature of the gas is 25 degrees celsius c)at STP the molar volume of a gas is 22.4L d)at STP the molar volume of all gases are the same ...

**Chemistry(Please check)**

1) choose the correct statement about the postulates of kinetic theory of gases. a) a sample of a gas consists of a small number of large particles close together. b) the movement of gas molecules is predictable, not random. c) when gas molecules collide, they permanently ...

**Algabra A(1)**

a solution of 67% soution is mixed with a solution o f57% to make 30 liters of a 59% solution. How many of each solution is used?

**algebra**

i need help

**math**

Swimsuit discounted 65% on sale for $20.30. what was the original price?

**Physics**

The angular speed of a propeller on a boat increases with constant acceleration from 12 rad/s to 26 rad/s in 2.5 revolutions. What is the acceleration of the propeller?

**physics13**

Find the mass of each of these weights in kg (a) 97 N (b) 83 N (c) 1.03 N

**physics12**

The instruments attached to a weather balloon have a mass of 5.1 kg. (a) The balloon is released and exerts an upward force of 102 N on the instruments. What is the acceleration of the balloon and instruments? (b) After the balloon has accelerated for 13 seconds, the ...

**physics10**

A sled of mass 51 kg is pulled along snow-covered, flat ground. The static friction coefficient is 0.30, and the sliding friction coefficient is 0.10. (a) What does the sled weigh? (b) What force will be needed to start the sled moving? (c) What force is needed to keep the ...

**physics9**

You are driving a 2460.0-kg car at a constant speed of 19.0 m/s along an icy, but straight and level road. While approaching a traffic light, it turns red. You slam on the brakes, Your wheels lock, the tires begin skidding, and the car slides to a halt in a distance of 27.0 m...

**physics8**

Your new motorcycle weighs 2411 N. What is its mass in kilograms?

**physics7**

A 81.0-kg (179 lb) boxer has his first match in the Canal Zone (g = 9.782 m/s2) and his second match at the North Pole (g = 9.832 m/s2). (a) What is his mass in the Canal Zone? (b) What is his weight in the Canal Zone? (c) What is his mass at the North Pole? (d) What is his ...

**physics6**

A 64-kg boy and a 42-kg girl use an elastic rope while engaged in a tug-of-war on an icy frictionless surface. If the acceleration of the girl toward the boy is 3.5 m/s2, determine the magnitude of the acceleration of the boy toward the girl.

**physics5**

A race car has a mass of 707 kg. It starts from rest and travels 40 m in 4.0 s. The car is uniformly accelerated during the entire time. What net force is applied to it?

**physics4**

After a day of testing race cars, you decide to take your own 1540-kg car onto the test track. While moving down the track at 12 m/s, you suddenly accelerate to 27 m/s in 9 s. What is the average net force that you have applied to the car during the 9-s interval?

**physics3**

when a karate strike hits wooden blocks, the hand undergoes an acceleration of -6500 m/s2. Medical data indicates the mass of the forearm and hand to be about 0.7 kg. What is the force exerted on the hand by the blocks?

**physics2**

A 873 kg (1930 lb) dragster completed the 402.0 m (0.2498 mile) run in 4.950 s. If the car has constant acceleration, what would be its acceleration and final velocity?

**physics**

A 880-kg (1945 lb) dragster, starting from rest, attains a speed of 27.3 m/s (61.0 mph) in 0.60 s. (a) Find the average acceleration of the dragster during this time interval? (b) What is the size of the average force on the dragster during this time interval? (c) Assume the ...

**us history**

what do you think were the 15 most important events in us history between the founding of jamestown(1600's) and the end of the great depression (1930's)???

**english**

"big and solid as twelve pounds of mashed potatoes in an eight-pound bag" is an example of what?

**Physics**

Thanks but that just made me more confused.

**Physics**

The space shuttle has a weight 2.00 x 10^7 N. The shuttle is accelerated upward at a rate of 5.50 m/s^2. What is the mass of the shuttle? What is the thrust (force) of the combined engines? What is the magnitude of the net force applied to the space shuttle?

**psychology**

the effects of mood and gender on proxemics

**science**

Earths mass is 6 x 10^24kg and its radius is 6.38 x 10^6m (6380 km ). Use the inverse-square law to show that in space-shuttle territory, 200 km above the earths surface the force of gravity on a shuttle is about 94% of that at the earths surface.

**Chemistry**

1) what mass of oxygen will react with 2.64g of magnesium? 2Mg + O2 -> MgO I was going to do 2.64g * (1/2) from the equation but im not sure. Do I have to add a 2 in front of the MgO? 2) How many moles of sodium ions are present in 2.50 L of 0.300 M Na3PO4? I know M=moles/L...

**Chemistry**

For #2 I got 55.41 from (.5184 * 106.9051) so 55.41 + 0.4816x = 107.87 -55.41 -55.41 then divide by 0.4816 The answer is 108.91amu but I did not get this.

**Chemistry**

1) How many miles are covered in a 15km race? (1 mile=5280, 12 in=1 ft, 1in=2.54cm) I know that I have to convert but I do not know where to start. 2) Silver (107.87amu) has two naturally occuring isotopes. In a typical sample, 51.84%of silver exists as Ag-107 (106.9051 amu). ...

**Chemistry**

oh i see thank you!!!

**Chemistry**

I know the answer for protons is 45 and electrons 50 but i do not understand where that came from

**Chemistry**

1)How many protons and electrons are in a sulfate ion SO4^2- ? I know the answer is 48 protons and 50 electrons but i do not know how to get this from the ion. 2) What is the charge on a sulfide ion? The answer is -2 but im not sure why. Is sulfide always -2?

**Chemistry(Please help)**

Disregard

**Chemistry(Please help)**

1)How many protons and electrons are in a sulfate ion SO4^2- ? I know the answer is 48 protons and 50 electrons but i do not know how to get this from the ion. 2) What is the charge on a sulfide ion? The answer is -2 but im not sure why. Is sulfide always -2?

**Physics**

Well I know density is equal to mass/volume. So I guess find both! I know that doesn't really help at all (I'm taking physics too so I understand) but maybe going back to simplicity can help! Sorry!

**us history**

What was Scott Joplin most known for duirng the 1920's? please do not just give me a url to a site with his biography because i have already looked at many! I am trying to narrow my answer down to 3 sentences. thanks!

**5TH GRADE MATH**

the rule is subtract 8. I'm not sure if that's what you're asking or not but that's my answer! Hope it helped:D

**french**

I have a project where I have to make a video about the differences between arts in USA and in Alsace, France. Arts meaning painting, sculpture, music that kind of thing. I have been try to research but have not come up with much. I don't really know what to search and ...

**Animal Science**

I need a statistic of how many dogs and cats are currently in a foster home in the us. Does anyone know a website that has this credible statistic? thanks

**math**

how would i find the area of the parallelogram if the area of each right triangle region is 7 1/2 square inches

**Algebra (direct variation)**

the value of y varies directly with x, and y=-2 when x=-4 Find y when x=8 -2=k(-4)