Select the correct answer.
why does every chemical reaction require a certain amount of activation energy?
o a
energy is released when the reactants begin to react.
o b. energy lost to the environment during the reaction must be replaced.
oc forming the activated complex requires energy.
od. the products have more potential energy than the activated complex.
o e.
the reactants have less potential energy than the products.

The first one

Explanation:

Out of those I'd say the first ones the most right, chemical bonds have to be broken to start a chemical reaction which is exothermic and does release energy.

So yea the top one I reckon.

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.