Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.480 g and then makes several scratches in the copper coating (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s)+2hcl(aq)→h2(g)+zncl2(aq) the student collects the hydrogen produced over water at 25 ∘c. the collected gas occupies a volume of 0.903 l at a total pressure of 785 mmhg .

calculate the percent zinc in the penny. (assume that all the zn in the penny dissolves.)

The percent of zinc in the penny is 96.84%.

Explanation:

Volume of the hydrogen gas = 0.903 L

Pressure of hydrogen  gas = P

P = total pressure  - Water's vapor pressure at 25°C

P = 785 mmHg - 23.8 mmHg = 761.2 mmHg

1 atm = 760 mmHg

761.2 mmHg = 1.0016 atm

Temperature of the gas = T = 25°C = 298.15 K

Moles of hydrogen gas collected = n

(ideal gas equation )

According to reaction , 1 mol of hydrogen gas is given by 1 mol of zinc.

Then 0.03695 moles of hydrogen gas will be given by:

of zinc

Mass of 0.03695 moles of zinc = 0.03695 mol × 65 g/mol= 2.4016 g

Percentage of zinc in 2.480 grams of penny:

2b2t

explanation:

2b2t

the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.