Question 6
how many grams of h 2 will be produced if 26.9 ml of 0.254 m hcl solution are combined with excess mg metal? the reaction is 2 hcl + mg > h2
+ mgcl2

0.00610 g H₂

The equation for the reaction;

2HCl(aq) + Mg(s) → H₂(g)+ MgCl₂(aq)

Given;

Volume of HCl = 26.9 mL or 0.0269 L

Molarity of HCl = 0.254 M

We need to calculate the mass of H₂ produced

Moles = Molarity × Volume

Moles of HCl = 0.254 M × 0.0269 L

                      = 0.00683 moles

from the Equation 2 moles of HCl reacts to produce 1 mole of Hydrogen gas

Therefore; Mole ratio of HCl to H₂ is 2 : 1

Moles of H₂ = 0.00683 moles ÷ 2

                   = 0.003415 moles

Mass = Number of moles × molar mass

Molar mass of H₂ = 2.02 g/mol

Therefore;

Mass of H₂ = 0.003415 moles × 2.02 g/mol

                 = 0.00610 g

Therefore, mass of hydrogen gas produced is 0.00610 g

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).