• Q : Problem based on mass collected in container....
    Chemistry :

    A sample of N2(g) was collected over water at 25 degrees Celcius and 730 torr in a container with a volume of 340 mL. The vapor pressure of water at 25 degrees Celcius is 23.76 torr. What mass of N2

  • Q : Half-life of a radioactive element....
    Chemistry :

    If the half-life of a radioactive element is 30.0 years, how long will it take for a sample to decay to the point where its activity is 70.0% of the original value?

  • Q : Nuclear chemistry and half lives....
    Chemistry :

    Rhenium-186 is a ß-emitter with a half-life of 90.0 hours. How long would it take for the activity in a sample of this isotope to decay to exactly one-third of its original value?

  • Q : What is the molar solubility of cerium....
    Chemistry :

    The solubility product for cerium(III) fluoride is 8.0 x 10^-16 (A) what is the molar solubility of Cerium (III) Fluoride in water?

  • Q : What is the value of n for the cell reaction....
    Chemistry :

    At 298 K a cell reaction has a standard emf of +0.17 V. The equilibrium constant for the cell reaction is 5.5 105. What is the value of n for the cell reaction?

  • Q : Calculate the wavelength of the electron....
    Physics :

    A scanning electron microscope operating at an accelerating voltage of 10 kV accelerates electrons to 20% of the speed of light, calculate the wavelength of the electron.

  • Q : Find the mass of the given substance....
    Chemistry :

    Question: An unknown mass of each of the following substances, initially at 24.0 C, absorbs 1920 J of heat. The final temperature is recorded as indicated. Find the mass of each substance.

  • Q : Compute the volume....
    Chemistry :

    Calculate the volume (in mL) of a 1.22 M Na2S solution needed to react with 2.75 g of AlBr3 (molar mass = 266.7 g/mol) in the following reaction:

  • Q : Kinetics and rate laws....
    Chemistry :

    Would the calculated value of k, the true rate constant, be in error if the concentration of dye was actually doubled the value you were told? Explain your answer.

  • Q : Determine the pressure of the gas....
    Chemistry :

    A cylinder containing 23.5 moles of nitrogen gas has a volume of 9.81L. What is the pressure of the gas at 23°C?

  • Q : What is the mass of the gold in grams....
    Chemistry :

    A chunk of gold with an unknown mass is heated to 163 degrees C and dropped into 38.0 grams of water at 25.0 degrees C. If the final temp of the water is 36.5 degrees C, what is the mass of the gold

  • Q : Element crystallizes in a body-centered cubic lattice....
    Chemistry :

    An element crystallizes in a body-centered cubic lattice. The edge of the unit cell is 2.52 \AA, and the density of the crystal is 6.11 {\rm g/cm^3}

  • Q : What mass in grams of hydrogen is produced by the reaction....
    Physics :

    What mass in grams of hydrogen is produced by the reaction of 4.73 g of magnesium with 1.83 g of water?

  • Q : Problem based on electromagnetic radiation....
    Physics :

    The average distance between Mars and Earth is about 1.3 x 10^8 miles. How long would it take TV pictures transmitted fromt he Viking space vehicle on Mars' surface to reach Earth? ( 1 mile = 1.61 k

  • Q : What is the partial pressure of carbon dioxide....
    Chemistry :

    Carbon dioxide is dissolved in an aqueous solution at 303 K at a concentration of 0.90 x 10-4 kg/kg. Henry's Law constant at these conditions is 0.186 x 104 atm. What is the partial pressure of CO2 in

  • Q : Pairs of elements containing polar covalent bonds....
    Chemistry :

    Which of the binary compounds formed by the following pairs of elements contain polar covalent bonds?

  • Q : Calculate the final volume of the ballon....
    Chemistry :

    A gas filed ballon having a volume of 2.50L at 1.2 ATM and 20 degrees celcius is allowed to rise to the stratosphere where the temperature and pressure are -23 degrees celcius and 3.00 x 10^-3 atm r

  • Q : Calculate the number of moles of gas in the sample....
    Chemistry :

    A sample of nitrogen in a 4.5L container at a temperature of 27 degrees C exerts a pressure of 4.1 atm. Calculate the number of moles of gas in the sample.

  • Q : Reaction of sodium bicarbonate with hydrochloric acid....
    Chemistry :

    Sodium bicarbonate is reacted with concentrated hydrochloric acid at 37.0°C and 1.00 atm. The reaction of 6.00 kg of bicarbonate with excess hydrochloric acid under these conditions will produce

  • Q : Reverse osmosis process....
    Chemistry :

    A reverse osmosis unit is used to obtain drinkable water from a source that contains 0.870 g NaCl per liter. What is the minimum pressure (in torr) that must be applied across the semipermeable memb

  • Q : Calculate the standard emf....
    Chemistry :

    Calculate the standard emf at 25°C of the propane fuel cell given that delta G° formation for propane = -23.5 kJ/mol. The overall reaction for the fuel cell is:

  • Q : What is the molarity of the ferric hydroxide solution....
    Chemistry :

    In a titration, 35.84 mL of 0.2419 M HCl solution is required to completely neutralize 18.62 mL of Fe(OH)3 solution. What is the molarity of the Fe(OH)3 solution?

  • Q : Ph of the solution after certain minutes....
    Physics :

    A current of 10.7 A is applied to 1.25 L of a solution of 0.554 M HBr converting some of the H+ to H2 (g), which bubbles out of solution. What is the pH of the solution after 68 minutes?

  • Q : Pressure and temperature based problem....
    Physics :

    A gas occupies 85ml at 0°C and 710 torr. What temperature would be required to increase the pressure to 760 torr with the volume remaining constant?

  • Q : Lowest energy photons visible to the human eye....
    Physics :

    The lowest energy photons visible to the human eye have energy 164 kJ/mol. What is the wavelength of such a photon, in nm?

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