draconis

At what temperature will silver have a resistivity that is two times the resistivity of copper at room temperature?

Two metal balls A and B of negligible radius are floating at rest on Space Station Freedom between two metal bulkheads, connected by a taut nonconducting thread of length 2.75 m. Ball A carries charge q, and ball B carries charge 2q. Each ball is 1.56 m away from a bulkhead.

(a) If the tension in the string is 2.60 N, what is the magnitude of q? (Ignore any contribution from induced charge in the bulkheads.)

(b) What happens to the system as time passes? Explain. (Assume the thread is oriented perpendicular to the bulkheads.)

Fifty milliliter (50.0 ml) samples of each of pairs of solutions are combined. Which pair forms a buffer?

Select one:

a. 0.200 M HNO2 and 0.300 M KOH

b. 0.200 M HBr and 0.100 M NaOH

c. 0.300 M HNO2 and 0.200 M KOH

d. 0.100 M HBr and 0.200 M NaOH

e. None of these pairs form buffers.

I have two questions that I cant figure out

1) [log4] x+[log4](x+2)=[log4]8

2) f(x)=1/2x^2+6x-3 : find the vertex using -b/2a

4.199 g of NaF(s) are dissolved in water and poured quantitatively into a 25.00 mL volumetric flask which is filled to the line with DI water and mixed well. 10.00 mL of this solution is pipetted into a 100 mL volumetric flask which is filled with DI water and mixed well. 20.00 mL of this solution is pipetted into a 100 mL volumetric flask which is filled with DI water and mixed. What is the [NaF] in this final solution?

Suppose coffee that id at 170 F is poured into a mug and allowed to cool in a room where the temp is 70F. The Temp T in (degrees F) of a coffee at time t ( in minutes) can be modeled by

T(t)=70+100e^-0.045t

According to the model when will the temperature of the coffee be 120 F?

How to solve? Just plugging in different values for t I came up with around 15 minutes it will be 120.91 (closest I could get) but I know there is an easy and accurate way to do this. Please help!!

According to the US Census Bureau the population of the world in 2012 was 7018 million people. In addition , the population of the world was growing at a rate of 1.26% per year. Assuming the growth rate continues, the model

P(t)=7018(1.0126)^t-2012

According to this model , what will the population of the world be in 2015 and 2025?

Is it just like solve for t? How do you do this. Help please!

Calculate the molar mass of an unknown molecular compound mixed with solid camphor, C10H16,O, heated and then cooled giving the following data:

Mass of unknown=0.195g

Tf (camphor)= 179.8 C

Kf (camphor) = -40.0 C/m

Mass camphor= 25.03 g

Tf (solution)= 176.7 C

Please help!

The freezing point of benzophenone: 49.9 C

Freezing point of benzophenone + unknown = 42.9

Mass of benzophenone in solution = 5.701 g

Mass of unknown in solution = 0.550

Value of Kfp for benzophenone= - 9.80 degrees C

Solution was heated to 80 C and then cooled.

This is all the information I have.

Should the answer for the depression be 7 degrees? Help me calculate molality of solution and solute please. I also need to find the molar mass of the unknown. Any guidance would be appreciated.

f(x) = sqrt(x^2+5x-14/x-1)

I think the answer should just be (-inf,1)u(1,inf) but I dont know how to get there. Please help

Max has 15 yards of fencing to make a rectangular kennel for her dog. He will build the kennel next to his house h=so he only needs to enclose three sides. What dimensions maximize the area of the kennel? What is the maximum area?

How would I set this up in an equation?

It takes john 2 hours longer than frank to mow the same lawn. if it takes them 5 hours to mow it working together , how long does it take frank to mow it alone?

I got F=7.5 hours

J= 9.5 hours

I'm not sure I'm doing it right though. Please assist.

A small plane travels 400 miles with the wind and turns around and does the trip against the wind. The plane flies 150 mph in still air. If it takes the plane 2 hours longer against the wind, how fast was the wind blowing?

I dont know how to even start the process. Please help.

I am not sure how this is supposed to be set up:

Flip 5 coins 200 times.You should have 6 expected classes. Get your expected ratio from Pascal’s triangle Keep a tally sheet. Do a chi square. Do your data fit expections?

http://shazam.econ.ubc.ca/flip/

I also have a table that comes with this that says Class in one column then Expected and Observed. So I'm supposed to have 6 classes ? How do I set up the triangle?

Albinism in humans is controlled by a recessive gene (c). Suppose two heterozygous individuals (genotype Cc) marry. Assume they have six children.

A. What is the probability that at least one child will be albino?

I know each child has 25% chances of being albino I think but dont know where to go from there.

B. What is the probability that three will be albino and three will have pigmentation?

C. A challenge: What is the probability that three of the children will be boys AND all three boys will be albino? Hint assume gender is independent of whether or not a child turns out to be albino.

If the 2.0 M HCl reagent bottle actually contained 4.0 M HCl, what effect would this have on the experimental results when variable amounts of Mg were added to 10.00 mL portions of HCl(aq)?

Select one:

a. No effect.

b. Slope of initial linear line would be cut in half.

c. Transition from one limiting reactant to the other would occur after less Mg is added.

d. Transition from one limiting reactant to the other would occur after more Mg is added

e. Slope of initial linear line would double.

If 220 mL of gas were collected from the reaction of 1.250 g of a Zn-KCl mixture, what is the percent Zn in the mixture? (At the same temperature and pressure, the Mg/HCl reaction gave 24.2 L gas/mol Mg.)

Select one:

a. 17.7 %

b. 95.2 %

c. 35.3 %

d. 23.8 %

e. 47.6 %

If several large air bubbles entered the graduated cylinder filled with water when it was inverted into the water trough, what would the effect be on a plot of volume H2(g) vs. mass Mg?

1. The slope of the volume vs. mass Mg line would be higher than without any air.

2. The intercept of the volume vs. mass Mg line would be higher than without any air.

3. The slope of the volume vs. mass Mg line would be the same as without any air.

4. The intercept of the volume vs. mass Mg line would be the same as without any air.

Select one:

a. I and IV

b. II and III

c. III and IV

d. I and II

e. None of these pairs of effects are valid.

If 0.654 g of Zn(s) reacted with 20.00 mL of a 2.00 M HCl(aq) solution until no more H2(g) was observed to form, what is the concentration of HCl(aq) or the moles of Zn2+(aq) remaining in the 20.00 mL of solution?

Select one:

a. 1.5 M HCl

b. 1.0 M HCl

c. 0.005 mol Zn2+(aq)

d. 0.5 M HCl

e. 0.010 mol Zn2+(aq)

C(s) + CO2(g) ----> 2CO(g) Note: The heat of sublimation of graphite,C(s), is 719 kJ/mol

I cant figure out the answer. Help me solve this please!

How many orbitals are there in an atom with the following combinations of quantum numbers?

1) n= 3, l= 2

2) n= 4, l= 2, mt= 2