A train's horn produces a $148-\mathrm{Hz}$ sound while moving at $32.0 \mathrm{~m} / \mathrm{s}$. What frequencies are heard by a person standing still beside the tracks as the train approaches and after it passes?

Molybdenum metal must absorb radiation with a minimum frequency of

$$1.09 \times 10 ^ { 15 } \mathrm { s } ^ { - 1 }$$

before it can eject an electron from its surface via the photoelectric effect. What wavelength of radiation will provide a photon of this energy?

Molybdenum metal must absorb radiation with a minimum frequency of

$$1.09 \times 10 ^ { 15 } \mathrm { s } ^ { - 1 }$$

before it can eject an electron from its surface via the photoelectric effect. What is the minimum energy needed to eject an electron?

A water desalination plant is set up near a salt marsh containing water that is 0.10 M NaCl. Calculate the minimum pressure that must be applied at $20 ^\circ$ to purify the water by reverse osmosis. Assume that NaCl is completely dissociated.

The molar heat of vaporization of ethanol is $39.3 \mathrm{~kJ} / \mathrm{mol}$, and the boiling point of ethanol is $78.3^{\circ} \mathrm{C}$. Calculate $\Delta S$ for the vaporization of $0.50$ mole of ethanol.

$\mathrm{B}_2 \mathrm{Br}_4$ has the following staggered structure: Show that $\mathrm{B}_2 \mathrm{Br}_4$ has one less plane of symmetry than $\mathrm{B}_2 \mathrm{~F}_4$ which is planar.

At liftoff, the space shuttle uses a solid mixture of ammonium perchlorate and aluminum powder to obtain great thrust from the volume change of solid to gas. In the presence of a catalyst, the mixture forms solid aluminum oxide and aluminum trichloride and gaseous water, and nitrogen monoxide.
(b) How many total moles of gas (water vapor and nitrogen monoxide) are produced when $50.0 \mathrm{~kg}$ of ammonium perchlorate reacts with a stoichiometric amount of $\mathrm{Al}$ ?

At liftoff, the space shuttle uses a solid mixture of ammonium perchlorate and aluminum powder to obtain great thrust from the volume change of solid to gas. In the presence of a catalyst, the mixture forms solid aluminum oxide and aluminum trichloride and gaseous water, and nitrogen monoxide.
(a) Write a balanced equation for the reaction, and identify the reducing and oxidizing agents

Glowing hydrogen gas from stars, such as the sun, emits specific frequencies of light. However, the frequencies of the light observed from stars in distant galaxies are lower than expected. Construct an explanation for this phenomenon.

After determining the frequency of the waves in the previous problem, you then use a handheld sonar system to determine the ocean depth at $10.0-\mathrm{m}$ increments from the shore. The data are shown in the table. Complete the table and construct a graph of the wave speed as a function of the depth.

At the beach, you time wave crests hitting the shore and determine there are 20 seconds between crests. Determine the frequency of the wave. Would you expect this frequency to change if you made your measurements further out from the shore?

You take 20.0 g of a sucrose $\left( \mathrm { C } _ { 12 } \mathrm { H } _ { 22 } \mathrm { O } _ { 11 } \right)$ and $\mathrm { NaCl }$ mixture and dissolve it in 1.00 L of water. The freezing point of this solution is found to be $- 0.426 ^ { \circ } \mathrm { C } .$ Assuming ideal behavior, calculate the mass percent composition of the original mixture and the mole fraction of sucrose in the original mixture.

A boy throws a baseball onto a roof and it rolls back down and off the roof with a speed of 3.75 m/s. If the roof is pitched at $35.0^{\circ}$ below the horizon and the roof edge is 2.50 m above the ground, find the horizontal distance from the roof edge to the point where the baseball lands on the ground.

You are testing a sonar machine underwater by sen ding out sound waves to measure distances. Using the graphical representations shown for the wave, find the amplitude, frequency, wavelength, and speed of the wave, and write a mathematical representation of the wave.