Calcium hydride (CaH2) reacts with water to form hydrogen gas: CaH2(s) + 2 H2O(l) → Ca(OH)2(aq) + 2 H2(g) Determine the number of grams of CaH2 are needed to generate 55.0 L of H2 gas at a pressure of 0.811 atm and a temperature of 32°C.\

Explanation:

Hello,

In this case, since the undergoing chemical reaction is:

By knowing the gas data of hydrogen, we can compute the formed moles by considering the ideal gas equation as:

In such a way, since hydrogen and calcium hydride have a 2 to 1 molar relationship in the chemical reaction, the number of grams of calcium hydride turns out, by means of stoichiometry:

Best regards.

m = 37.5373 g

Explanation:

To do this, let's write the reaction again:

CaH₂(s) + 2H₂O(l) > Ca(OH)₂(aq) + 2H₂(g)

In this reaction we can see that the mole ratio of CaH₂ and H₂ is 1:2, in other words:

moles CaH₂/moles H₂ = 1/2

We need to know how many grams of CaH₂ reacted to form 55 L of Hydrogen. to do this, we need to know how many moles of Hydrogen were produced. and as Hydrogen is a gas, and we know the volume and pressure of it, we can use the ideal gas equation to solve for the moles of hydrogen:

PV = nRT      solvinf for the moles:

n = PV / RT

R is constant of gases and is 0.082 L atm /mol K and the temperature is 32 °C (305 K) so, the moles are:

n = 0.811 * 55 / 0.082 * 305

n = 1.7835 moles

We have the moles, let's calculate the moles of CaH₂ used with the mole ratio of before:

moles CaH₂/moles H₂ = 1/2

moles CaH₂ = moles H₂/2

moles CaH₂ = 1.78 / 2 = 0.89175 moles

Finally the mass is calculated using the molecular mass of CaH₂ which is 42.094 g/mol, so the mass is:

m = 0.89175 * 42.094

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j

they are both synthetic elements

explanation:

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