During a laboratory experiment, a 3.81-gram sample of nahco3 was thermally decomposed. in this experiment, carbon dioxide and water vapors escape and are combined to form carbonic acid. after decomposition, the sample weighed 2.86 grams. calculate the percentage yield of carbonic acid for the reaction. describe the calculation process in detail. nahco3 → na2co3 + h2co3

The % yield is 24.4%. See below for details.

Explanation:

First balance the chemical formula:

2NaHCO3 --> Na2CO3 + H2CO3

Next calculate the moles of NaHCO3 at the beginning and end by dividing by molar mass:

Initial: 3.81 / 84 = 0.045 mol

Final: 2.86 / 84 = 0.034 mol

Change (actual amount reacted): 0.045 - 0.034 = 0.011 mol

You can see based on the original chemical formula that for every 2 moles of NaHCO3 that react, only 1 mole of H2CO3 is produced. Therefore, you will need to divide each NaHCO3 value by 2 to find the corresponding value of H2CO3. In this case we are most interested in the initial amount of NaHCO3 (since this represents the maximum possible amount of reactant, and therefore product, we can have - the theoretical amount of product), and the change in NaHCO3 (since this is the amount of reactant that actually reacted):

Theoretical H2CO3: 0.045 / 2 = 0.0225 mol

Actual H2CO3: 0.011 / 2 = 0.0055 mol

The percent yield is calculated from these two values (you could convert back to mass if you wanted but it wouldn't change the answer):

% yield = actual / theoretical

% yield = 0.0055/0.0225

% yield = 24.4%

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.

it's c. elements are placed in rows based on how may valencies electrons have.