A chemist makes a solution of Mg(NO3)2 by dissolving 21.3 g Mg(NO3)2 in water to make 100.0 mL of solution. What is the concentration of NO3− ions in the solution? Assume that Mg(NO3)2 is the only solute in the solution. The molar mass of Mg(NO3)2 is 148.33 g/mol.

Answer : The concentration of is, 2.88 M

Explanation : Given,

Mass of = 21.3 g

Volume of solution = 100.0 mL

Molar mass of = 148.33 g/mole

First we have to calculate the concentration of

Molarity : It is defined as the number of moles of solute present in one liter of volume of solution.

Formula used :

Now put all the given values in this formula, we get:

The concentration of is, 1.44 M

Now we have to calculate the concentration of

As, 1 mole of dissociates to give 1 mole of ion and 2 mole of ion.

So, 1.44 M of dissociates to give 1.44 M of ion and (2 × 1.44 M = 2.88 M) of ion.

Thus, the concentration of is, 2.88 M

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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.