Lecture 139/30/05

Quiz 4 1. Balance the following reaction: Fe(s) + H 2 O(g)  Fe 3 O 4 (s) + H 2 (g) 2. If you begin with 3.0 moles of Fe and 3.0 moles H 2 O, how many moles of H 2 can be formed?

Solutions: concentrations

How to prepare a solution?

Dilution of a concentrated solution moles = moles M 1 V 1 = M 2 V 2

Dissolve 5.00 g of NiCl 2 6 H 2 O in enough water to make 250 mL of solution. Calculate molarity.

Prepare 400 mL of 2.00 M HNO 3 from concentrated nitric acid (16M)

Some properties of gases 1. Gases can be compressed 2. Can exert pressure on whatever surrounds them 3. Expands into whatever volume is available 4. Mix completely with one another

What is pressure? Pressure = Force/Area Units of pressure: mm Hg (from early barometers) 760 mm Hg at sea level Torr (after Evangelista Torricelli) 760 mm Hg = 760 Torr PSI (pounds per square inch) Atmosphere (atm) Pascal = newton/m 2 Newton = 1 kg-m/s 2 Bar = 10 5 Pa 1 atm = 760 mm Hg = 760 Torr = kPa = bar=14.7 PSI

Rank the following in decreasing order of magnitude: 75 kPa 250 mm Hg 0.83 bar 0.63 atm

Hg rises in tube until: Force(Hg) = Force(atmosphere) Force(down) = Force(up) Pressure of Hg related to: Hg density column height

Compare the heights of a Hg barometer and a water barometer if atmospheric pressure is 1 atm. (Density of Hg = g/cm 3 )

A scuba diver taking photos of a coral reef 60 ft below the ocean surface breathes out a stream of bubbles. What is the total gas pressure of the bubbles at the moment they are released? What is the pressure when the bubbles get to the surface? DUE MONDAY