The zinc within a copper-plated penny will dissolve in hydrochloric acid if the copper coating is filed down in several spots (so that the hydrochloric acid can get to the zinc). the reaction between the acid and the zinc is as follows: 2h+(aq)+zn(s)→h2(g)+zn2+(aq). when the zinc in a certain penny dissolves, the total volume of gas collected over water at 25 ∘c was 0.955 l at a total pressure of 742 mmhg .

The amount of hydrogen gas collected will be 0.074 g

Explanation:

We are given:

Vapor pressure of water = 23.78 mmHg

Total vapor pressure = 742 mmHg

Vapor pressure of hydrogen gas = Total vapor pressure - Vapor pressure of water = (742 - 23.78) mmHg = 718.22 mmHg

To calculate the amount of hydrogen gas collected, we use the equation given by ideal gas which follows:

where,

P = pressure of the gas = 718.22 mmHg  

V = Volume of the gas = 0.955 L

T = Temperature of the gas =

R = Gas constant =

n = number of moles of hydrogen gas = ?

Putting values in above equation, we get:

To calculate the mass from given number of moles, we use the equation:

Moles of hydrogen gas = 0.037 moles

Molar mass of hydrogen gas = 2 g/mol

Putting values in above equation, we get:

Hence, the amount of hydrogen gas collected will be 0.074 g

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !