In order to prepare very dilute solutions, a lab technician chooses to perform a series of dilutions instead of measuring a very small mass. A solution was prepared by dissolving 0.360 g of KNO3 in enough water to make 500. mL of solution. A 10.0 mL sample of this solution was transferred to a 500.0-mL volumetric flask and diluted to the mark with water. Then 10.0 mL of the diluted solution was transferred to a 250.0-mL flask and diluted to the mark with water. What is the final concentration of the KNO3 solution?

7.91 × 10-9 M
5.70 × 10-6 M
2.85 × 10-6 M
7.12 × 10-3 M
1.42 × 10-4 M

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.

you did not give any options thus this is the best answer i can give to you with this little information you have given

> they are both natural and not man made

> they can be tracked and predicted by the right tools

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answer; the numbers of valence electrons in the acetic acid molecule (ch3co2h) is 24;