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 0.947 L at a total pressure of 740 mmHg. What mass of hydrogen gas is collected?

The amount of hydrogen gas collected will be 0.073 g

Explanation:

We are given:

Vapor pressure of water = 23.78 mmHg

Total vapor pressure = 740 mmHg

Vapor pressure of hydrogen gas = Total vapor pressure - Vapor pressure of water = (740 - 23.78) mmHg = 716.22 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 = 716.22 mmHg  

V = Volume of the gas = 0.947 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 = 0.0365 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 0.073 g

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

the answers would be

the first one and the second one