Homework Help

Instant cold packs used to treat athletic injuries contain solid NH4NO3 and a pouch of water. When the pack is squeezed, the pouch breaks and the solid dissolves, lowering the temperature because of the following endothermic reaction. NH4NO3(s) + H2O(l) = NH4NO3(aq) deltaH = +25.7 kJ What is the final temperature in a squeezed cold pack that contains 50.0 g of NH4NO3 dissolved in 115 mL of water? Assume a specific heat of 4.18 J/(g·°C) for the solution, an initial temperature of 25.0°C, and no heat transfer between the cold pack and the environment. To find the mass of water use the density of water = 1.0 g/mL. Hint: The process takes place at constant pressure. …

Hi all , I may have created a similar thread before but I am sorry I need help again and this is a bit diffrent to before. I recently did a gel electrophoresis experiment, and now I need to find out the mass of the unknown protein sample. For that I have been given MW markers that were run alongside the DNA (TE) and the E1 which contains the unknown protein sample. So my question is that would I need to plot the migration of the E1 fragments against the size of the MW marker on a semi-log paper to estimate the mass of the unknown protein sample? There are total 7 bands shown in the gel image for the MW marker, and thier sizes are 97.2, 66, 44, 29, 20, 14.…

Hi can someone please help me on this, i need some ideas on this. My practical was on 'detection of antiviral antibodies in serum using an ELISA technique'. We followed the basic ELISA method of detecting antibodies in two patients serum. The test was for measles, mumps, rubella, and cytomegalovirus. From the results I found that patient 1 tested positive for mumps and rubella but negative for measles and cytomegalovirus. And patient 2 tested positive for measles and rubella but negative for mumps and cytomegalovirus. Both of them tested negative for cytomegalovirus and both positive for rubella. I am now writing the discussion bit, and I am supposed to discuss …

why xray is used in compton effect rather than uv ray?

Envision a minor motor-vehicle accident. Car X backs out of a parking space at 1.000m/s toward the east. Car Y, whose driver searches for a place to park, travels north at 1.000m/s. Neither driver sees the other car, and the cars collide. Suppose that each car (including its driver) has a mass of 1000kg. The total system momentum vector before the collision is approximately? a) 1000kg x m/s toward the northeast. b) 1414 kg x m/s toward the northeast. c) 2000kg x m/s toward the northeast. d) zero, because the vehicles haven't hit each other yet! My text book has been teaching me with formulas of momentum. However, when i attempted it by finding the momenutm of e…

Hi everyone, I have a problem about full binary tree like this: Find the number of internal vertices, terminal vertices and the hight of a full binary trees have a total of 7 vertices. I calculate the number of internal vertical is 3 and the number of terminal vertices is 4, i think it is ok. However, i am not sure about the height of this full binary tree, i try to draw and calculate the height can be 2 or 3 but i saw someone draw for a full binary tree have 7 vertices in the website http://www.maths.usyd.edu.au/u/kooc/catalan/cat13ftree.pdf, they pointed out that the height is only 3. Can you please explain more for me about the height of a full binary tree in this…

1) If A = [aij] is an n x n matrix, the trace of A, Tr(A), is defined as the sum of all elements on the main diagonal of A, Tr(A) = the sum of (aii) from i=1 to n. Show each of the following: a) Tr(cA) = cTr(A), where c is a real number b) Tr(A+B) = Tr(A) + Tr(B) c) Tr(A(Transpose)) = Tr(A) 2) If r and s are real numbers and A and B are matrices of the appropriate sizes, then proves the following: A(rB) = r(AB) =(rA)B I have been thinking these for a long time with no directions to approach. Please help!!!

All the terms are confusing me. How do histones, nucleosomes, solenoids and looped domains all fit into DNA packaging? :S:S

In ion exchange chromatography, how do you find the order of elution of proteins based on pI? I have a graph of KCl conc vs. fraction number and I have to find the conc of KCl required to elute some given proteins. And I'm given pI values of 4.6-4.9 for albumin and 6.8-7.8 for hemoglobin, and 10 -11 for cytochrome c, so what do I do with these numbers in relations to my KCl conc std curve and my ionic conductivity of fractions?

why there was a need of this wein displacement law? i mean to say why this law evolved?

I am attempting to use the Henderson Hasselbalch equation to calculate the pH of blood with a pCO2 of 41mmHg and a bicarb concentration of 20mM. I know how to do this problem but was not sure if I needed to convert mmHg to mM in order for the equation to work. I have been looking for conversion factors to do so but have been unsuccessful. Any suggestions are appreciated. Thanks.

I have a question on my exam revue that I am having a hard time with. Its probably really easy, but I can't figure it out. MY QUESTION When a solution containing 15.og of aluminum chloride is mixed with a solution containing 15.0g of sodium hydroxide, a double displacement reaction occurs. a) Predict the mass of aluminum hydroxide produced. b) What mass of the excess reagent remains unreacted? thanks for you help

Let C1 and C2 be circles in the plane. Describe the number of possible points of intersection of C1 and C2. It is 4?

What isthe net charge of your pentapeptide at physiological pH 7.4 and pH 1.5? This is my pentapeptide: ala-leu-glu-hos-his. N-terminus has a pk~9 glu has a pk~4 his has a pk~6 c-terminus has a pk~3 How do i determine what the charges are for each amino acid, so that i can determine my net Charge? Thank you Alex

solve each given linear system by the method of elimination 2x-3y+4z=-12 x-2y+z=-5 3x+y+2z=1 How to solve this problem. What should I do first?

Hello, I'm a high school student and I have to design my own experiment but I need some help. I am making my own activated carbon and testing how well it filters water of impurities by dying some sort of chemical, putting it in water, filtering the solution through the activated carbon, and testing the remaining solution using a spec 20 to see how well the carbon filtered it. My question is, what are possible chemicals that I can dissolve in the solution that the carbon can filter out, and what type of dyes would work well to dye this chemical? Your help is EXTREMELY appreciated!!! Thank you!

My Maths teacher thinks that there is no such thing as 12am or 12pm... That according to his 'Maths Texts' they are only called Midday or Midnight - we've tried to prove him wrong but he is standing steadfast... Does anyone here have any answers to his 'theory'? And if so, do you have any proof that I would be able to show him??? Thanks, LT

Like the description says, I need help isolating h from: mgh = k(h-l-L)²/2 I'm almost certain that the quadratic formula needs to be used to isolate h, but I'm not sure how to use it (haven't used it since grade 9). Thanks!

Thanks.

Hello everybody, Today is my first day on science forum. I am studying in 9th std. I came upon the following question in my text book, which I was unable to answer. So I am posting this on the scince forum, seeking your help. The question is- "During which situation may an object dropped from a certain height not fall to the earth?" Thanks and regards.

Hi Folks, I am having a devil of a time understand the concept of input work vs input force (relating to machines). OK -- I get that you push down a car's pedal and the car moves. Your force is vastly increased by the car's engine. The input force is much much less than the output force. The car has a mechanical advantage of some factor. But I don't understand how this isn't the same terminology as work. If my input work is pushing the pedal, the car still moves the same amount. The amount of work done by the car is a huge amount more than mine. Sure, my work is the same, but the ouput work is much more than the input work. What am I missing her…

Hi, given that Cs+ has 55 protons and electronic configuration of 2.8.18.18.8, and Cl- has 17 protons and electronic configuration of 2.8.8, why is the ionic radii of Cl- (0.181nm) > ionic radii of Cs+ (0.167nm)? I know that Cs+ has many more protons than Cl-, which means that the pulling force on the electrons in Cs+ is much greater than that on those in Cl-, but what about Cs+ having many more layers of electrons than Cl-? Which has more significance in determining ionic radii, the pulling force on electrons, or the number of layers of electrons? Is there a 'sure' way to determine whether Cs+ or Cl- (or any two ions in different groups and periods, for the ma…

I've got a chemistry exam coming up and am struggling to understand balancing the chemical equation for a redox reaction. Just getting started with breaking it down to 2 half equations is what im stuck on. If anyone has any simple ways it would be much appriciated Thanks

in H2AsO4-. I figured it was four, but I am mistaken. Any pointers?

Hi, I'm doing some biology homework on genetic variation, and I'm kinda stuck! Well so the case is this: Maize plants that were grown from purple grains had cobs that had all purple grains. When fully grown, the resultant plants were self pollinated, giving these results in the cobs produced: Purple grains: 1836 Red grains 578 White grains 772 I have been given a hint that the alleles are: R - red, r - colourless, E - purple, e - colourless, and am supposed to draw a genetic diagram to show the cross described... From the ratio of purple:red:white grains, I'm pretty sure it is recessive epistasis, yet i'm not sure of the relationship between the all…