Gold (111) chloride
calcium carbonate
hydrobromic acid
what’s the formulas to these compounds

Explanation:

Gold (111) Chloride:

AuCl₃

The oxidation state of gold is +3.

Chlorine is present in group seventeen and have seven valance electrons . Thus it accept one electron to complete the octet and show oxidation state -1.

When it react with gold(III) three chlorine atoms are combine with one gold atom to make compound overall neutral.

Calcium Carbonate:

CaCO₃

Carbonate formula is CO₃²⁻ . It means it carry -2 charge . Calcium is present in group two. It has two valance electrons and lose them to get complete octet thus shows +2 oxidation state.

When it combine with carbonate the overall compound is neutral because -2 and +2 charges cancel each other.

Hydrobromic Acid

HBr

Hydrogen has one electron while bromine has seven valance electrons. Bromine require one more electron to complete the octet. It react with hydrogen by sharing of one electron of hydrogen and form polar covalent compound.

precipitation

explanation:

when it goes from cloud to rain/back to earth in the form of rain

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.