Sodium hydride racts with excess water to produce
aqueoussodium hydroxide and hydrogen gas. what mass (in grams) of
sodiumhydride will produce 982 ml of gas at 28.0 c and 765 torr,
when thehydrogen fas is collected above water? the vapor pressure
of waterat this experiment is 28 torr.

0.96g of sodium hydride

Explanation:

Equation of reaction:

NaH + H20 = NaOH + H2

Mass of hydrogen gas produced (m) = PVM/RT

P = 765torr - 28torr = 737torr = 737/760 = 0.97atm, V = 982mL = 982cm^3, M = 2g/mol, R = 82.057cm^3.atm/gmol.K, T = 28°C = 28 + 273K = 301K

m = (0.97×982×2)/(82.057×301) = 0.08g of hydrogen gas

From the equation of reaction

1 mole (24g) of sodium hydride produced 1 mole (2g) of hydrogen gas

0.08g of hydrogen gas would be produced by (24×0.08)/2 = 0.96g of sodium hydride

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e