Tuesday
September 2, 2014

Posts by bob


Total # Posts: 2,374

AQA Mechanics (M1), Statics and forces,please help
The diagram shows a cylinder of mass 20 kg lying at rest on two smooth planes inclined at angles of 40 degree and 50 degree to the horizontal. Calculate the reaction force exerted by the planes on the cylinder. For digram, please click the following link
March 19, 2012

chemistry
If HClO2 is a stronger acid than HF, which is stronger than HOCl, then the order of strengths of the conjugate bases of these acids is ______ < _____ < _____ a) ClO- < F- < ClO2- b) ClO2- < ClO- < F- e) F- < ClO2- < ClO- c) ClO- < ClO2- < F- d) ...
March 17, 2012

chemistry
The Ka for HOBr is 2.4 x 10-9. Thus, you can report the pKb for OBr– as a) 4.2 x 10-6 b) 9.62 c) 5.38 d) 8.62 e) 1.38 help!
March 17, 2012

chemistry
Which salt below will dissolve in water to yield an acidic solution? a) NaNO2 b) K C§¤O4 c) NH4NO3 d) Na2CO3 e) Mg Br2 help!
March 17, 2012

chemistry
The approximate pH of a 3.0 x 10-3 M solution of the strong acid H2SO4 is a) 3.5 b) 3.0 c) 2.5 d) 2.2 e) -3.0 how do you do this?
March 17, 2012

chemistry
The ion HPO4–2 has both a conjugate base as well as a conjugate acid. The conjugate base of this ion is (1) while the conjugate acid is (2). a) (1) = H2PO4– (2) H3PO4 b) (1) = PO4– (2) H2PO4+ c) (1) = PO4–3 (2) H2PO4– d) (1) = HPO5–3 (2) HPO3–...
March 17, 2012

chemistry
Which of the following is a Bronsted-Lowry base but not a Lewis base? a) H2O c) CN– e) all choices are both a B/L and Lewis base. b) CO3–2 d) NH3 need help deciding
March 17, 2012

chemistry
Which of the following is not amphiprotic? a)H2O c)NH4+ e)all choices are amphiprotic b)HSO4 – d)H2PO4– need help!
March 17, 2012

english
In The Secret, the secret is found in a a conversation. b letter. c line of poetry. d newspaper column. I think a
March 13, 2012

chemistry
Using this data, 2 NO(g) + Cl2(g) == 2 NOCl(g) Kc = 3.20 X 10-3 NO2(g) == NO(g) + ½ O2(g) Kc = 3.93 calculate a value for Kc for the reaction, NOCl (g) + ½ O2 (g) == NO2 (g) + ½ Cl2 (g) A. 20.2 B. 2.06 X 10-4 C. 4.49 D. 4.84 X 10-3 E. 0.223 eliminated down...
March 12, 2012

chemistry
Using this data, 2 NO(g) + Cl2(g) == 2 NOCl(g) Kc = 3.20 X 10-3 NO2(g) == NO(g) + ½ O2(g) Kc = 3.93 calculate a value for Kc for the reaction, NOCl (g) + ½ O2 (g) == NO2 (g) + ½ Cl2 (g) A. 20.2 B. 2.06 X 10-4 C. 4.49 D. 4.84 X 10-3 E. 0.223 eliminated down...
March 12, 2012

physics
A child moves with a speed of 5.40 m/s when positioned 14.0 m from the center of a merry-go-round. Calculate the net force (in newtons) exerted on the child, whose mass is 26.0 kg.
March 12, 2012

chemistry
when you reverse it do you get a negative?
March 12, 2012

chemistry
Using this data, 2 NO(g) + Cl2(g) == 2 NOCl(g) Kc = 3.20 X 10-3 NO2(g) == NO(g) + ½ O2(g) Kc = 3.93 calculate a value for Kc for the reaction, NOCl (g) + ½ O2 (g) == NO2 (g) + ½ Cl2 (g) A. 20.2 B. 2.06 X 10-4 C. 4.49 D. 4.84 X 10-3 E. 0.223 eliminated down...
March 12, 2012

Math
A bag has 4 red, 6 white, and 9 blue marbles. How many ways can 5 marbles be selected if 2 are one color, and 3 are another color?
March 12, 2012

PHi103
The truth table for a valid deductive argument will show
March 11, 2012

math
(4.35E-2 - x)(7.56E-2 -x ) ============================ (0.324 + 2x)2 Rearrange to get an expression of the form ax2 + bx + c = 0 and use the quadratic formula (solve for x. This gives: x = 1.05E-2, 0.143 basically i understand they use the quadratic equation but how did they...
March 10, 2012

physics
a 25000000 gr rocket is propelled from rest by an engine that produces a 312500 kgm/s2 for 1.375s A) What is the sleds acceleration? B) What is the velocity after 1.375s?
March 7, 2012

Math :(
please answer......
March 6, 2012

Math :(
A rectangular pyramid with the base of 12 feet by 8 feet need to be filled with balloons. if the pyramid 16 feet tall, how much space is available for the balloons?
March 6, 2012

math
the outlier is 7 and the outlier is a number away from all the other ones,which in this case is 7.
March 6, 2012

math
Jean has 4 times as many marbles as Peter. If Jean gave 18 marbles to Peter, they would then have the same number of marbles. How many marbles does each have?
March 6, 2012

Chemistry
How many moles of nitric acid will be produced when .51 mole of dinitrogen pentoxide reacts
March 5, 2012

7th grade math
yes,Pi is an irrational number.
March 5, 2012

math
Determine the slope of a line passing through the points (2, 9) and (0.66, 9).
March 5, 2012

physics
Jabdbal
March 5, 2012

6th grade science
How do the surface proteins on a virus help it to invade a host cell?
March 4, 2012

Math
Parallel lines have the same slope so the slope of 3x-4y+5 =0 is y=(-3x-5)/-4 slope =3/4 therefore the y=(n-2)x+12 must have a slope of 3/4 so n-2=3/4 n=2.75 If the lines are perpendicular they have negative reciprocal slopes therefore n-2= -4/3 n=2-4/3 or 2/3
March 3, 2012

algebra
There are three important numbers coming from the factors, 0, -1, and 3 test using numbers around those numbers. Using -2 because it is less than -1 (-2)(-2+1)(-2-3) =-10 which is < 12 Using -.5 because it is between -1 and 0 (-.5)(-.5+1)(-.5-3)=.875 which is <12 Using 1...
March 3, 2012

Physics help?
A 170 -pF capacitor is connected in series with an unknown capacitance, and as a series combination they are connected to a battery with an emf of 25.0 V. If the 170 -pF capacitor stores 135 pC of charge on its plates, what is the unknown capacitance?
March 3, 2012

maths
Do the same thing you did before using -1/2 for x. (2x+1=0 and solve for x) Then you will have two equations and two unknowns and you can solve for p
March 3, 2012

math
x= total marbles x-(1/4)x what he had after 1st round (x-(1/4)x)-1/3(x-(1/4)x) what he had left after 2nd (x-(1/4)x)-1/3(x-(1/4)x)-1/2((x-(1/4)x)-1/3(x-(1/4)x)) what he had left after 3rd round which equals 2 (the one he gave to Shavana and the one he kept) (x-(1/4)x)-1/3(x-(1...
March 3, 2012

Math
When raising to a power multiply the exponents. 8.8*10^25
March 2, 2012

math 2nd grade
francisco (:
February 29, 2012

3 grade math
You body consist of 7/10 water. Is more than 1/2 your body water? Explain
February 29, 2012

5th grade Math
-3+5*(2(-6))=37
February 29, 2012

Trig
A pilot is flying over a straight highway. He determines the angles of depression to two mileposts, 6.7 mi apart, to be 36° and 41°, as shown in the figure
February 29, 2012

Physics
Smd
February 28, 2012

One Trigonometry Question Please Help!
8 1/2 inches long into 1/2 inches long will be how many short pecies
February 28, 2012

Math
Words
February 27, 2012

Mathematics
What percentage is 2/27?
February 27, 2012

Physics
A 73kg sprinter, starting from rest, reaches a speed of 7.0 m/s in 1.8s, with a negliable effect due to air resistance. The sprinter then runs with the remained of the race at a steady speed of 7.0 m/s under the influence of a 35-N force due to air resistance. What is the ...
February 27, 2012

Math
It equauls 2sinx
February 25, 2012

Math
How do I solve: sqrt(3)tanx= I need to use the identity tanx=sinx/cosx Thanks
February 25, 2012

chemistry
If the reaction Cl2 (g) + O3 (g) = Cl2O (g) + O2 (g) occurred in just two steps, what would be the overall order of the reaction be? a. 1 b. 2 c. 3 d. 4 e. not possible to determine from the information given help
February 25, 2012

chemistry
The equation A + 2 B = C + D describes an elementary reaction, which takes place in a single step. Thus, the rate law must be a. rate = k(A]2 b. rate = k(B]2 c. rate = k(A][B] d. rate = k(A][B]2 e. none of the above represents the rate law for this elementary reaction. help
February 25, 2012

chemistry
The decomposition of hydrogen peroxide in solution and in the presence of iodide ion was studied in laboratory, and the following mechanism proposed based on the experimental data. H2O2 + I - = H2O + IO - (slow) H2O2 + IO - = H2O + O2 + I - (fast) Which one of the following ...
February 25, 2012

chemistry
A particular reaction has an activation energy of 51.6 kJ/mol-rxn. How much faster is the reaction at 50 degrees C versus 25 degrees C? a. 2 times b. 5 times c. 3 times d. half as fast d. 20% as fast help No one has answered this question yet.
February 25, 2012

chemistry
For a one step reaction, the activation energy for the forward reaction is 40.0 kJ/mol and the enthalpy of reaction is -20.0 kJ /mol. Which statement below is true? a. The activation energy of the forward reaction would be affected to a greater extent than the activation ...
February 25, 2012

chemistry
If the reaction Cl2 (g) + O3 (g) = Cl2O (g) + O2 (g) occurred in just two steps, what would be the overall order of the reaction be? a. 1 b. 2 c. 3 d. 4 e. not possible to determine from the information given
February 24, 2012

chemistry
A catalyst alters the rate of a reaction by a. changing the products in the reaction. b. increasing the activation for the reaction. c. always providing a surface on which the molecules react. d. providing an alternate pathway for the reaction. e. increasing the concentrations...
February 24, 2012

chemistry
The equation A + 2 B = C + D describes an elementary reaction, which takes place in a single step. Thus, the rate law must be a. rate = k(A]2 b. rate = k(B]2 c. rate = k(A][B] d. rate = k(A][B]2 e. none of the above represents the rate law for this elementary reaction.
February 24, 2012

chemistry
The decomposition of hydrogen peroxide in solution and in the presence of iodide ion was studied in laboratory, and the following mechanism proposed based on the experimental data. H2O2 + I - = H2O + IO - (slow) H2O2 + IO - = H2O + O2 + I - (fast) Which one of the following ...
February 24, 2012

chemistry
The reaction: A + 3 B = D + F was studied and the following mechanism was finally determined A + B = C (fast) C + B = D + E (slow) E + B = F (very fast) The step with largest activation energy is a. the first step b. the second step c. the third step d. none of the steps has ...
February 24, 2012

chemistry
For a particular chemical reaction, the rate constant at 30.0 °C is 1.38 X 10-4 L mol-1 s-1, while the value at 49.0 °C is 1.21 X 10-3 L mol-1 s-1 . What is the activation energy for this reaction? a. 92.8 kJ b. 200 kJ c. 40.4 kJ d. 343 kJ e. 56.4 kJ ln 1.38x 10 -4 / 1...
February 24, 2012

chemistry
For a certain chemical reaction, the rate constant at 250.0 °C is 0.00383 s-1 and the activation energy is 22.40 kilojoules. Calculate the value of the rate constant at 335.0 °C. a. 0.00513 s-1 b. 0.00946 s-1 c. 0.00787 s-1 d. 0.0224 s-1 e. 0.000640 s-1 b or c
February 24, 2012

chemistry
For a one step reaction, the activation energy for the forward reaction is 40.0 kJ/mol and the enthalpy of reaction is -20.0 kJ /mol. Which statement below is true? a. The activation energy of the forward reaction would be affected to a greater extent than the activation ...
February 24, 2012

chemistry
A particular reaction has an activation energy of 51.6 kJ/mol-rxn. How much faster is the reaction at 50 degrees C versus 25 degrees C? a. 2 times b. 5 times c. 3 times d. half as fast d. 20% as fast help
February 24, 2012

Math/Calculus.
Suppose (x^2)*(e^(-2y))= ln(xy) Find dy/dx by implicit differentiation.
February 22, 2012

chemistry
how does the electrolyte paste in a battery work
February 22, 2012

math
I have a rectangle w/ 20 boxes in it what would 1/5 of the boxes be?
February 22, 2012

calculus
The voltage signal from a standard European wall socket can be described by the equation V(t)=325sin100 pi x , where t is time, in seconds and V is the voltage at time, t. determine the period frequency and amplitude
February 21, 2012

English
Tree
February 21, 2012

physics/chemistry
so it is a physics project
February 21, 2012

physics/chemistry
if i'm testing conductivity of different salts?
February 21, 2012

physics/chemistry
is conductivity a physical or chemical property
February 21, 2012

math
a data set of size 19 has correlation coefficient of r= 0.432. Test the significance of r at the 5% level and at the 1% level
February 19, 2012

geometry
In the figure below, the measure of arc AC is 88 degrees if angle ABC is equal to 88 degrees.
February 19, 2012

math
Write as a single log of a single argument: log3 24 + log3 17 - log3 51
February 17, 2012

Math
For a class play, student tickets cost $2 and adult tickets cost $5. A total os 30 tickets were sold. If the total sales must exceed $90, what is the miniuim number of adult tickets that must be sold?
February 17, 2012

chemistry
How many molecules of hydrogen gas are produced by the reaction of tin with 20.0 L hydrogen mono fluoride at STP
February 16, 2012

PHYICS HELP
While a person is walking, his arms swing through approximately a 45° angle in .530s. As a reasonable approximation, we can assume that the arm moves with constant speed during each swing. A typical arm is 70.0 cm long, measured from the shoulder joint. 1) What is the ...
February 15, 2012

Math
What's the answer to "230 is increased to 250?"
February 13, 2012

Physics
Henrietta is going off to her physics class, jogging down the sidewalk at a speed of 2.05 m/s. Her husband Bruce suddenly realizes that she left in such a hurry that she forgot her lunch of bagels, so he runs to the window of their apartment, which is a height 43.9 m above the...
February 8, 2012

chemistry
Consider the reaction below: Cgraphite(s) + F2(g) +1/2O2(g) → CF2O(g) Which of the following is a correct rate expression? 1. rate = −2∆[O2]/∆t 2. rate = −∆[CF2O]/∆t 3. rate =∆[F2]/∆t 4. rate = −∆[Cgraphite]/&#...
February 7, 2012

Chemistry
Carbon dioxide gas has a solubility of 0.0972 g/100 g H2O at 40 degrees celsius. Expressed in parts per million, this concentration is closest to... (1)0.972 ppm (2)9.72 ppm (3)97.2 ppm (4)972 ppm
February 7, 2012

geometry
A regular hexagon has side lengths 15 in. The perimeter of the hexagon is 90 in. A second hexagon has side lengths 18.75 in. Find the perimeter of the second hexagon. Round to the nearest tenth.
February 7, 2012

algebra
A box of animal crackers measures 12 inches by 8 inches by 2 inches. What is the volume of the box?
February 7, 2012

algebra
The sum of three consecutive integers is -96. What is the largest integer?
February 7, 2012

algebra
The sum of three consecutive integers is . What is the largest integer?
February 7, 2012

algebra
Ky has 3 times more books than Grant, and Grant has 6 fewer books than Jaime. If the total combined number of books is 176, how many books does Jaime have?
February 7, 2012

math - integers
68 kms
February 7, 2012

Mathg
8*2=16. Answer is 8.
February 6, 2012

math
Side of Square is 25 feet. One side of rectangle is 30 feet and other is 20 feet.
February 6, 2012

math
512
February 6, 2012

math
72
February 6, 2012

math
35*6 is 210 not 200.
February 6, 2012

physics
in 1989 michel menin of france walked on a tightrope suspended under a balloon nearly at an altitude of 3150 m above the ground . suppose a coin falls from menin's pocket during his walk . how high above the ground is the coin when its speed is 60 m/s ?
February 6, 2012

physics
the largest watermelon ever grown had a mass of 118 kg. suppose this watermelon were exhibited on a platform 5 m above the ground . after the exhibition, the watermelon is allowed to slide along to the ground along a smooth ramp, How high above the ground is the watermelon at ...
February 6, 2012

physics
A Physics book , mass unknown , is dropped from a table . its velocity just before hitting the ground is 9.39 m/s . what is the height of the table ?
February 6, 2012

physics
a 20 kg rock is on the edge of a 100 m cliff . the rock falls from the cliff , what is its kinetic energy just before it hits the ground ?
February 6, 2012

materials science
A bar of pure nickel is coupled with a bar of pure iron (interfaced). The diffusion couple is then heated to a temperature of 1000°C. (a) How long will it take for the concentration of nickel to reach 0.1 wt%, 1.0 μm below the interface? (b) How long will it take for ...
February 6, 2012

geometry
ABCD is a trapezoid with DC parallel to AB, AB=4, AD=4, angle A=60, angle C=45. Find DC and BC
February 3, 2012

chemistry
In a nickel bath with a total volume of 1000 gallons, titration of a 50 milliliter sample with 0.1 N silver nitrate used up 10.5 milliliters to the end point. What is the concentration in ounces per gallon of the nickel chloride (NiCl2 ) in the bath?
February 3, 2012

chemistry
A 10 milliliter sample of HCl pickle is titrated with 0.2 N NaOH to a phenol-phthalein end point and it is found that 6.5 milliliters are used. What is the concentration of HCl in the Pickle in grams per liter? In weight Percent?
February 3, 2012

math
Bob and Jack play a shooting game. In this game, they have a net at a distance. The net is made up of 1 mm thick wires. The wires run vertically and horizontally to form a mesh that has 5 mm square openings between them. A bullet 2 mm in diameter must be shot in such a way ...
February 1, 2012

calculus
actually an ODE question(but there's no diff. eq. subforum) (y^2)(dy/dx)+y^3/x =2/x^2 using substitution u(x)=y^3 so I've been doing a few of these and getting them all wrong and this problem... I don't know where to start. I tried (1/u)(du/dx)+u/x(du/dx)=2/x^2 but...
January 30, 2012

materials science
Consider a copper lattice with an excessive average of one vacancy in every 100 unit cells. What will be its density? Compare this to the theoretical density of copper.
January 30, 2012

Chemistry
How many grams of CO2 are formed when 32 g of O2 reacts with 23 g of C2H5OH?
January 29, 2012

algebra
parking lot had a length that is 7 yards greater than thre width. the area of the lot is 450 square yards. what is the length and width?
January 29, 2012

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