<u>Answer:</u> The average rate of the reaction is 
<u>Explanation:</u>
To calculate the molarity of hydrogen gas generated, we use the equation:

Moles of hydrogen gas = 
Volume of solution = 250 mL = 0.250 L (Conversion factor: 1 L = 1000 mL)
Putting values in above equation, we get:

Average rate of the reaction is defined as the ratio of concentration of hydrogen generated to the time taken.
To calculate the average rate of the reaction, we use the equation:

We are given:
Concentration of hydrogen generated = 0.1564 M
Time taken = 20.0 minutes
Putting values in above equation, we get:

Hence, the average rate of the reaction is 
The formula for water is H2O so there would have to be two Hyrdogens and one oxygen. Therefore it would be 4g of Hydrogen and 16g of Oxygen leaving you with 20g.
The answer is D.
Hope this helps :) ~
Answer:
It works because of the significant principle of piezoelectricity
Explanation:
3.5 M has 3.5 moles per litre
so we have one litre, so we need 3.5 moles
moles = mass/molarmass
3.5 * 23 = 80.5