In order to determine the rate of photosynthesis (the conversion by plants of carbon dioxide and water into glucose and oxygen), the oxygen gas emitted by an aquatic plant is collected over water at a temperature of 293 K and a total pressure of 754.8 mmHg. Over a specific time-period, a total of 1.31 L of gas is collected. The partial pressure of water at 293 K is 17.55 mmHg. What mass of oxygen gas (in grams) forms

1.6896 grams

Explanation:

Given that:

Total pressure = The pressure of   + partial pressure of

∴

The pressure of    = Total pressure - partial pressure of

= (754.8 - 17.55) mmHg

= 737.25 mmHg

At standard conditions:

1 mmHg = 0.00131579 atm

∴

737.25 mmHg will be: (737.25*0.00131579) atm = 0.970065928 atm

P ≅ 0.97 atm

The temperature  (T) = 293 K

Volume (V) = 1.31 L

Using ideal gas equation

PV = nRT

0.97 × 1.31 = n × 0.0821 × 293

n = 0.0528

mass of oxygen   = no. of moles * molar mass

= 0.0528 * 32

= 1.6896 grams

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .