Tuesday
May 26, 2015

Posts by danny


Total # Posts: 776

Maths
Have a question on complex numbers. Z1= 1+j2, Z2= 2+j5 Find total impedance in Cartesian and polar form of two impedances in parallel: 1/ZT = 1/Z1 + 1/Z2 I get to 39/58 + 83/58 j but then get a bit lost.
May 20, 2015

chemistry
What mass of solute is contained in 250 mL of 0.895 M NH4Cl? I think that this is a molarity question. Molarity = mass of solute/volume of solution in L. 1 mL = 0.001 L so 250 mL * 0.001 L = 0.25 L 0.895 M = X (mass of solute)/ 0.25 but since the answer is to be in grams, I ...
May 7, 2015

Economics
can someone help me put (yuan depreciates against the dollar into one stanza of a song.
May 5, 2015

physics
A fixed mass of gas has a pressure of 8700 Pa, a volume of 10.5 m3 and temperature of 68 °C. The pressure and volume of the gas are changed to 9 243 Pa and 14.4 m3. The new temperature of the gas is
May 4, 2015

chemistry
An atom whose nucleus contains 7 neutrons and which has a mass number of 12 is an isotope of what element?
April 27, 2015

chemistry
What is the approximate effective nuclear charge for arsenic ?
April 27, 2015

chemistry
q4 What element has the greatest first ionization energy? Li Na K Rb Cs
April 27, 2015

chemistry
Consider an electrochemical cell based on the reaction: 2H+(aq) + Sn(s) = Sn2+(aq) + H2(g). Which of the following actions would NOT change the measured cell potential? lowering the pH in the cathode compartment addition of more tin metal to the anode compartment any of the ...
April 19, 2015

chemistry
What is the oxidation state of the vanadium atom in VO4−
April 16, 2015

chemistry
Consider an electrochemical cell based on the reaction: 2H+(aq) + Sn(s) = Sn2+(aq) + H2(g). Which of the following actions would NOT change the measured cell potential? lowering the pH in the cathode compartment addition of more tin metal to the anode compartment any of the ...
April 16, 2015

chemistry
Which element is reduced in the unbalanced reaction below? I− + MnO4− + H+ = I2 + MnO2 + H2O I no reduction occurred in this reaction O H Mn
April 16, 2015

chemistry
How many electrons does the Au+ ion have ? Enter an integer below without any letters or symbols.
April 15, 2015

Physics
I have a question on fluids. Water in a section 1.2m wide, 2m high. retained by sluice gate that can pivot about its base. There is a retaining cable at the top of the gate. Determine tension in the retaining cable at the top of the gate when the depth of water is 1.8m. ...
April 13, 2015

Mechanical Principles
I have a question on fluids. Water in a section 1.2m wide, 2m high. retained by sluice gate that can pivot about its base. There is a retaining cable at the top of the gate. Determine tension in the retaining cable at the top of the gate when the depth of water is 1.8m. ...
April 13, 2015

Physics
Is this correct?? Metal block weighs 500g in air and 446g completely submerged in water. Calculate density and relative density. Density of water = 1000kg/m3 BF (Buoyant force) will be 500g-446g = 0.54 g (or 0.054 kg). For volume: If BF = Density(water)*V*g then V = BF/density...
April 10, 2015

Chemistry
Laughing gas (nitrous oxide, N2O) is sometimes used as an anesthetic in dentistry. It is produced when ammonium nitrate is decomposed according to the reaction NH4NO3(s) −! N2O(g) + 2H2O(§¤) . How much NH4NO3 is required to produce 54.5 g of N2O? Answer in ...
April 9, 2015

Chemistry
027 (part 1 of 3) 10.0 points Copper reacts with silver nitrate through single replacement. If 3.03 g of silver are produced from the reaction, how much copper(II) nitrate is also produced? Answer in units of mol. 028 (part 2 of 3) 10.0 points How much Cu is required in this ...
April 9, 2015

Chemistry
Calculate the mass of water formed by the complete reaction of 572 g of propane (C3H8) with excess oxygen. (Write a balanced equation.) Answer in units of g.
April 9, 2015

Mechnical principles
Mtal block weighs 500g in air and 446g completely submerged in water. Calculate density and relative density. I know relative density is density of material/density of water (1000kg/m-3)
April 9, 2015

chemistry
At a certain elevation, the boiling point of water is 98.5°C. How much energy is needed to heat 35.0 mL of water to the boiling point at this elevation if the water initially was at 23.4°C? (Cp=75.38J/(mol*C), d= 1.00g/mL)
April 1, 2015

Calculus 1
How do you find the derivative of 1/3(x^2+2)^3/2 ? Please help
March 31, 2015

physics
A 5.0 Ω resistor, a 9.0 Ω resistor, and a 12.0 Ω resistor are connected in parallel across a 24.0 V battery. a) What is the equivalent resistance of the circuit? Answer in units of Ω b) What is the current in the 5.0 Ω resistor? Answer in units of A
March 23, 2015

chemistry
The average swimming pool has a volume of about 28,000 gallons. Suppose a swimming pool was filled with pH 7.00 water. However, you need to adjust the pH to 4.75. How much acid pool acid (which is 1.00 M HCl) do you need to add to the pool? The units are liters. convert ...
March 21, 2015

chemistry
You need to determine the pKa of a weak, monoprotic acid. You add 0.500 moles of the acid to 1.00 L of water. The resulting pH was 1.87. What is the pKa of this weak acid? You may ignore the autoionization of water. 2.74 3.43 5.38 2.01 1.87
March 21, 2015

chemistry
ok so i think its hcl/nacl
March 21, 2015

chemistry
All of the following acid-base pairs are examples of buffers EXCEPT: (Question from "Cracking the MCAT, 2010-2011 edition" by The Princeton Review) HCl/NaCl CH3CO2H/NaCH3CO2 HF/NaF H2CO3/NaHCO3 I chose ch3co2h/nach3co2
March 21, 2015

chemistry
is the answer 9.86923
March 21, 2015

chemistry
What is the pH of 500 mL of water that had 0.00150 grams of NaOH added to it? The units are pH units with an error interval of 0.1 units. 0.00150 divided by 40NaOH 3.75e-5 divided that by 500= 7.5e-8 -log7.5e-8 =7.12 im lost on the last step
March 21, 2015

chemistry
The Ka of hypochlorous acid (HClO) is 3.00×10-8 at 25.0°C. Calculate the pH of a 0.0385 M hypochlorous acid solution. a.1.41 b.7.52 c.-1.41 D.4.47 E. 8.94 I got B 7.52 but i feel like im wrong
March 21, 2015

chemistry
A 300 mL solution of 0.0500 M HCl is titrated with 1.00 M KOH. How many mL of the KOH solution will be needed to reach the equivalence point of this titration? A.5 mL B.10 mL C.50 mL D20 mL E15 mL The answer i got was E. 15ml
March 21, 2015

chemistry
Which of the following acids is expected to be the strongest acid? CH2F-COOH CF3-COOH CH3-COOH CCl3-COOH CBr3-COOH i chose ccl3-cooh
March 21, 2015

chemistry
Which of the following chemicals are bases or can behave like bases? You may select more than one compound. KOH PO43- NH3 F-
March 21, 2015

chemistry
Which of the following chemicals are bases or can behave like bases? You may select more than one compound. Cu2+ RbOH CH3COO- Br-
March 21, 2015

chemistry
Which of the following chemicals are strong bases? You may select more than one compound. CH2=CH2 Ca(OH)2 NH3 RbOH
March 21, 2015

chemistry
I think i figured it out 0.0385 change -x. . . . .. . +x. . . .+x at equilibrium 0.0385-x. .. x..... . .x Ka = 3.0 x 10^-8 = [H+][ClO-]/ [HClO]= (x)(x)/ 0.0385-x x = [H+]= 3.4 x 10^-5 M pH = - log 3.4 x 10^-5=4.5 Im going with D now
March 21, 2015

chemistry
The Ka of hypochlorous acid (HClO) is 3.00×10-8 at 25.0°C. Calculate the pH of a 0.0385 M hypochlorous acid solution. A.1.41 B.7.52 C.-1.41 D.4.47 E.8.94 I chose B
March 21, 2015

physics
How many kilometers would you have to go above the surface of the earth for your weight to decrease to 39{\rm \\%} of what it was at the surface? Express your answer using two significant figures.
March 9, 2015

physics
A highway curve with radius 1000ft is to be banked so that a car traveling 56.0mph will not skid sideways even in the absence of friction At what angle should the curve be banked?
March 9, 2015

Physics
A baseball player with a mass of 79 kg slides into homeplate. The coefficient of kinetic friction between the player and the ground is μk = 0.632. If the player comes to rest after 1.04 s, what is his initial speed?
March 4, 2015

Calculus Physics
help anyone
March 2, 2015

Calculus Physics
Imagine a spaceship on its way to the moon from the earth. Find the point, as measured from the center of the earth, where the force of gravity due to the earth is balanced exactly by the gravity of the moon. This point lies on a line between the centers of the earth and the ...
March 2, 2015

Calculus Physics
A glass of orange juice is on the floor of a subway car traveling along a straight path at constant velocity. Everything's fine. The coefficient of static friction between the glass and the floor is 0.32. The subway suddenly accelerates forward. What is the maximum ...
March 2, 2015

chemistry
One of the ways to produce iron is to take iron(II) oxide and react it with carbon monoxide to get pure iron and carbon dioxide. The reaction is FeO(s) + CO(g) = Fe(s) + CO2(g). What is the partial pressure of CO2(g) if 2.00 atm of CO and excess iron(II) oxide are used to ...
February 28, 2015

chemistry
Lead iodide is a relatively insoluble compound. It can dissolve from the solid phase into the aqueous phase with a Keq of 0.00027. If the concentration of lead iodide in the aqueous phase 0.125 M, then: a. we need more information to determine the progress of the reaction. b. ...
February 28, 2015

chemistry
Equilibrium is: a dynamic condition in which the concentration of the reactants is equal to the concentration of the products. a static condition in which the concentration of the reactants is equal to the concentration of the products. a static condition in which the rate of ...
February 28, 2015

Science check
Water in the upper zones of the ocean will have more oxygen than water in deeper zones. true or false i think true.
February 27, 2015

math
6528
February 27, 2015

physics
PART ONE: A charge of 4.70μC is at the origin and a second charge of −2.85μC is on the positive x-axis 1.08 m from the origin. Find the magnitude of the electric field at a point P on the y-axis 0.640 m from the origin. The value of the Coulomb constant is 8.99...
February 26, 2015

chemistry
increase the temperature ?
February 25, 2015

chemistry
The following equilibrium exists in a closed container: N2(g) + O2(g) = 2NO(g), ΔH = +181 kJ/mol. Which of the following perturbations would favor the formation of NO(g)? (practice MCAT question from The Princeton Review MCAT Science Workbook, 2009 edition) increasing the...
February 25, 2015

chemistry
Suppose you have the following reaction at equilibrium: N2(g) + 3H2(g) = 2NH3(g), ΔH = −22 kcal/mol What changes are expected to occur if the temperature of the system was decreased. You may select multiple answers. The concentration of NH3(g) would decrease The ...
February 25, 2015

chemistry
1) C2H2O4(aq) = H+ (aq) + C2HO4- (aq); Keq = 6.5E-2 2) C2O42- (aq) + H+ (aq) = C2HO4- (aq); Keq = 1.64E+4 then what is the equilibrium constant for the following reaction: C2H2O4(aq) = 2H+ (aq) + C2O42- (aq)? Keq = 1070 Keq = 227 Keq = 2.21E-4 Keq = 3.96E-6 Keq = 6.30E-3
February 25, 2015

chemistry
The pollutant NO is formed in diesel engines. The reaction fixes atmospheric nitrogen with oxygen to form NO. The reaction is: N2(g) + O2(g) = 2NO(g). If the equilibrium constant for this reaction at elevated temperatures is 5.60E-11, then what is the partial pressure of NO ...
February 25, 2015

chemistry
How is the reaction quotient used to determine whether a system is at equilibrium? The reaction is at equilibrium when Q > Keq. At equilibrium, the reaction quotient is undefined. The reaction quotient must be satisfied for equilibrium to be achieved. The reaction is at ...
February 25, 2015

chemistry
Which of the following statements is not true? 1.Chemical equilibria are examples of reversible processes. 2.When multiple reaction steps are in equilibrium, then the equilibrium constant for the net reaction is the product of the individual reactions. 3.The equilibrium ...
February 25, 2015

Calculus Physics
Nevermind I figured it out
February 19, 2015

Calculus Physics
A 1559-kg car moves at 15.0 m/s. What is the magnitude of the horizontal net force needed to bring the car to a halt in a distance of 50.0 m?
February 19, 2015

Calculus Physics
Thanks Steve
February 19, 2015

Calculus Physics
That's F(t)=5sqrt(t)
February 19, 2015

Calculus Physics
A particle is subject to a time-dependent force: F(t)=5t√. If the particle's mass is 7 kg, what will its velocity be at t=6.7 seconds, assuming its initial velocity at t=0 is equal to 0.
February 19, 2015

Calculus Physics
A particles with mass 3.7 kg moves in the x direction according to the following function: x(t)=−7+4t+3t2−4t3. (the units of each coefficient are meters, and time is measured in seconds). At time t=7.8, what is the net force acting on the particle?
February 18, 2015

Calculus Physics
A box and one force vector, F1 is shown. F1 = + 10 N. If the mass of the box is 3 kg, what is the magnitude and direction of a force, F2, that would need to be applied if the box was to have an acceleration of + 2 m/s 2 in the horizontal direction. (Indicate direction by ...
February 18, 2015

physics
38. A rock of mass 0.400 kg is released from the surface and sinks in the ocean. As the rock descends it is acted upon by three forces: gravity, buoyancy, and drag. The buoyancy is an upward force equal to half its weight. Drag from the water can be modeled by F = kv, where k...
February 17, 2015

physics
21. A traffic signal of mass 25.0 kg is suspended by two cables as shown in the diagram below. Solve for the tension in each cable each of the following scenarios: (a) θ1 = θ2 = 20.0°, and (b) θ1 = 20.0°, θ2 = 30.0°.
February 17, 2015

chemistry
Two-stroke motor boat engines emit a large amount of partially burned fuel into the water. One of the more common chemicals is phenanthrene . The degradation half-life of phenanthrene is about 7.30 days in clear surface waters. If a motor boat emits 97.0 g of phenanthrene ...
February 15, 2015

chemistry
Based on reaction kinetics, which of the following pairs of reactions and reaction rate equations represent elementary reactions? You may choose more than one reaction. Ti + 2Cl2 = TiCl4 Rate = k[Ti][Cl2] 2SO2 + O2 = 2SO3 Rate = k[O2][SO2]2 Na2S + CuSO4 = CuS + Na2SO4 Rate = k...
February 14, 2015

chemistry
The activation energy of a reaction is typically determined by calculating the rate constant for the reaction at two temperatures and then manipulating the Arrhenius equation. If you determine the reaction rate constants for a particular reaction to be 0.0650 /s at 25.0 C and ...
February 14, 2015

chemistry
Suppose 100 moles of a chemical is spilled into a lake. After 15.0 days, the total amount of the chemical in the lake 3.50 moles. Assuming that the reaction followed first order kinetics and no chemical was lost due to advection or volatilization, then what is the rate ...
February 14, 2015

chemistry
Radioactive waste is difficult to dispose of due to the long time periods needed before the radiation effectively disappears. The US protocol is to store the waste for 10 half-lives of the material after which the waste is no longer considered radioactive. After this time, ...
February 14, 2015

chemistry
In which of the following reactions is ΔE closest in value to ΔH? HNO3(aq) + Na2(CO3)(aq) = NaNO3(aq) + H2O(l) + CO2(g) KClO3(s) = KCl(s) + (3/2)O2(g) HCl(aq) + NaOH(aq) = H2O(l) + NaCl(aq) Na(s) + H2O(l) = NaOH(aq) + (1/2)H2(g)
February 14, 2015

chemistry
If the breakdown half-life of a pesticide applied to a farmer’s field is 3.50 days, then what is the rate constant for this reaction? Assume the degradation reaction follows first order kinetics. The units are 1/d.
February 14, 2015

chemistry
Ethylene gas (C2H2) can be formed from the reaction of calcium carbide (CaC2) with water. What is the reaction rate if 14.2 grams of ethylene gas are produced over 4.00 seconds? The units are mol/s.
February 14, 2015

physics
REALLY NEED HELP WITH THIS PLEASE. One gram of palladium has 5.66×10^21 atoms, and each palladium atom has 46 electrons. How many electrons are contained in 7.00g of palladium? The elemental charge is1.6×10^−19C. Answer in units of electrons. The answer is 1....
February 8, 2015

physics
One gram of palladium has 5.66×10^21 atoms, and each palladium atom has 46 electrons. How many electrons are contained in 7.00g of palladium? The elemental charge is1.6×10^−19C. Answer in units of electrons. The answer is 1.82252x10^24 for Part A. i need help...
February 8, 2015

Physics
no the answer is incorrect. im so confused @bob
February 8, 2015

Physics
One gram of palladium has 5.66×10^21 atoms, and each palladium atom has 46 electrons. How many electrons are contained in 7.00g of palladium? The elemental charge is1.6×10^−19C. Answer in units of electrons. The answer is 1.82252x10^24 for Part A. i need help...
February 8, 2015

chemistry
Calculate the change in Gibb’s free energy when 1.63 moles of sodium metal react with excess chlorine gas to form sodium chloride . Assume standard conditions. The ΔG values can be found in your textbook. The units for the answer are kJ
February 7, 2015

chemistry
White phosphorus (P4) was used for a long time in military incendiary bombs and ordnances. White phosphorus reacts with oxygen in the air and burns at very high temperatures, so it sets things on fire. Calculate the change in enthalpy resulting from a 25.0 pound white ...
February 7, 2015

chemistry
Calculate the change in free energy when you drop 4.70 g of calcium metal into a beaker containing excess water so that Ca(OH)2(s) and H2 gas are formed? The delta-G values you need are in your textbook. The units are kJ.
February 7, 2015

chemistry
Which of the following processes is entropy increasing in the local system? You may select multiple processes. Combination reactions where two reactants join to make a single product. a system with increasing molecular motion cooling a six-pack of beer by putting it in a ...
February 7, 2015

chemistry
Which of the following reactions will be spontaneous at standard state? Not all the reactions are balanced, so make sure they are balanced first. The ΔG of formation data can be found in an appendix in your text book. You may select multiple answers. Any reaction with ...
February 7, 2015

chemistry
ΔS is positive for which one of the following reactions? Ag+(aq) + Cl- (aq) = AgCl(s) N2(g) + 3H2(g) = 2NH3(g) CaO(s) + CO2(g) = CaCO3(s) 2SO3(g) = 2SO2(g) + O2(g) H2O(l) = H2O(s)
February 7, 2015

chemistry
Suppose you have a reaction that has a ΔH of +80 kJ and a ΔS of 215 J/K. At what temperature will this reaction change from being not spontaneous to spontaneous? 31 C 99 C -18 C 25 C 53 C
February 7, 2015

Physics
huihillll
February 5, 2015

chemistry
Given the following values of ΔH, ΔS and T, calculate ΔG (in kJ). The values are: ΔH = 23.0 kJ, ΔS = 125 J/K, and temperature = 85.0 C.
February 5, 2015

chemistry
Given the following values of ΔH, ΔS and T, calculate ΔG (in kJ). The values are: ΔH = -95.0 kJ, ΔS = 217 J/K, and temperature = 160 C.
February 3, 2015

chemistry
How many core electrons are there in a ground state phosphorus atom?
February 3, 2015

chemistry
Given: Equation #1: 4NH3(g) + 5O2(g) = 4NO(g) + 6H2O; ΔH of reaction = -1170 kJ Equation #2: 4NH3(g) + 3O2(g) = 2N2(g) + 6H2O; ΔH of reaction = -1530 kJ Then what is the ΔH of reaction for: N2(g) + O2(g) = 2NO(g)? Enter a numerical value below and be sure to ...
January 31, 2015

chemistry
Calcium carbide (CaC2) reacts with water to form acetylene (C2H2) gas and calcium hydroxide (Ca(OH)2). If the ΔH for: CaC2(s) + 2H2O(l) = Ca(OH)2(s) + C2H2(g) is -127 kJ, then what is the enthalpy of formation for calcium carbide? The ΔH of formation for H2O(l), Ca(...
January 31, 2015

chemistry
Suppose that your morning shower is 7 minutes long and uses 4 gallons of water per minute that is a nice 102 F in temperature. How much energy (kJ) must be used to heat the water for your shower if the water coming into your house is at 60 F? The heat capacity of water is 4....
January 31, 2015

chemistry
Suppose you add 92 ml of dilute acid to 46 ml of water. Both the water and acid were at room temperature (22 C) before being mixed. The temperature of the solution increased to 39 C. How much energy (in kJ) was released by the dissolution of the acid if the specific heat ...
January 31, 2015

chemistry
In the reaction below, ΔH°f is zero for ___________. Ni(s) + 2CO(g) + 2PF3(g) = Ni(CO)2(PF3)2(l) Ni(s) CO(g) Ni(CO)2(PF3)2(l) both CO(g) and PF3(g) PF3(g)
January 31, 2015

chemistry
The enthalpy change for the following reaction is -483.6 kJ: 2H2(g) + O2(g) = 2H2O(g) Therefore, the enthalpy change for the following reaction is _______ kJ: 4H2(g) + 2O2(g) = 4H2O(g)
January 31, 2015

chemistry
What is the specific heat capacity of ethanol (C 2H 6O) if a 18.3 g sample increased 12.3 C upon the addition of 553.0 J? The units are J/(g ·K)
January 31, 2015

chemistry
The radiator in your car uses either water or ethylene glycol (anti-freeze) to remove heat from the engine and dissipate it to the outside air. If the water recirculation rate is 17.0 kg per minute of water and the water temperature leaving the engine and entering the ...
January 31, 2015

chem
What is the specific heat capacity of aluminum if a 8.4 g sample increased 21.1 C upon the addition of 159.0 J? The units are J/(g ·K). q=cpxMxT is the equation my answer i got is 401.65 is that right bec i feel thats wrong
January 29, 2015

chemistry 116
What is the specific heat capacity of aluminum if a 8.4 g sample increased 21.1 C upon the addition of 159.0 J? The units are J/(g ·K). q=cpxMxT is the equation my answer i got is 401.65 is that right bec i feel thats wrong
January 29, 2015

chem
The value for ΔH° for the reaction below is -72 kJ. How many kJ of heat are released when 1.0 mol of HBr is formed in this reaction? H2(g) + Br2(l) = 2HBr(g)
January 28, 2015

physics
What is the mass of 5.00L of pure water?
January 28, 2015

physics
A typical multivitamin tablet can contain 2.00mg of vitamin B2 (riboflavin), and the RDA is 0.0030 g/day. How many such tablets should a person take each day to get the proper amount of this vitamin, assuming that he gets none from any other sources?
January 28, 2015

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