# chemistry

posted by ayo

An 0.850 g sample of a mixture of LiH and CaH2 was reacted with H2O and the H2 gas produced, 1.20 L, was collected at STP. What mass % of the original mixture was LiH?

1. bobpursley

work it in two parts. let V be the volume of H2 produced in the CaH2 reaction, and 1.2-V be the volume in the LiH reaction. Let m be mass in the CaH2 reaction, and .850g -m be the mass in the LiH reaction.
You will get two equations, one unknown out of this.
CaH2 reaction:
CaH2 + 2H2O = Ca(OH)2 + 2H2
H2: P:1 atm T: 273K V: V
PV=nRT
nCa=PV/RT
n= (1*V)/(0.08206*273)
n= you do it.
LiH reaction:
same method, solve for NLi
you will get N in terms of V

now convert each of the N's to grams (by multiplying each by formaula masses of the hydrides), and set each to a funcion of m.
you should have time then to find the ratios of the two masses, and solve for percent. A bit of algebra is required.

2. DrBob222

LiH + H2O ==> LiOH + H2
CaH2 + 2H2O ==> Ca(OH)2 + 2H2
You must write two equations and solve them simultaneously. NOTE; ALL OF THESE NUMBERS ARE ESTIMATES; YOU SHOULD RECALCULATE ALL OF THEM.

Let Y stand for grams LiH.
and Z stand for grams CaH2.
Then equation 1 is Y + Z + 0.850

How many mols is 1.50 L @ STP. That's 1.50/22.4 = aprox 0.067
For the second equation you want to write an equation that equates mols H2 from LiH and mols H2 from CaH2 = 0.067

Below I will use mm for molar mass.

So mols H2 from LiH will be
[(Y/mm LiH)] x [(1 mol H2/1 mol LiH)]

and mol H2 from CaH2 will be
[(Z/mm CaH2)] x [2 mols H2/1 mol CaH2)]

Solve for Y = grams LiH.

Then % LiH = (g LiH/mas sample)*100
Post your work if you get stuck.

## Similar Questions

1. ### chem

Lithium hydride reacts with water as follows. LiH(s) + H2O(l) -->LiOH(aq) + H2(g) During World War II, U.S. pilots carried LiH tablets. In the event of a crash landing at sea, the LiH would react with the seawater and fill their …
2. ### Chemistry

A mixture of ethyne gas (C2H2) and methane gas (CH4) occupied a certain volume at a total pressure of 16.8 kPa. When the sample burned, the products were CO2 gas and H2O vapor. The CO2 was collected and its pressure found to be 25.2 …
3. ### AP Chemistry

A mixture of aluminum and zinc metal is used in 2 experiments described below: A- A 1.7 gram sample of the mixture is reacted with excess hydrochloric acid and the resulting hydrogen gas is collected over water. The reaction takes …
4. ### Chemistry

A 3.23 gram sample of a sodium bicarbonate mixture was reacted with excess acid. 48.52 mL of the evolved gas was collected of the water at .930 atm. and 23.0 degrees C. What is the percentage of sodium bicarbonate in the original mixture?
5. ### chm I

Lithium hydride reacts with water as follows. LiH(s) + H2O(l) -->LiOH(aq) + H2(g) During World War II, U.S. pilots carried LiH tablets. In the event of a crash landing at sea, the LiH would react with the seawater and fill their …
6. ### Physical Chemistry

A mixture of ethane and ethene occupied 35.5 L at 1.000 bar and 405 K. This mixture reacted completely with 110.3 g of O2 to produce CO2 and H2O. What was the composition of the original mixture?
7. ### Chemistry

A 1.00 g sample of enriched water, a mixture of H2O and D2O, reacted completely with Cl2 to give a mixture of HCl and DCl. The HCl and DCl were then dissolved in pure H2O to make a 1.00 L solution. A 25.00 mL sample of the 1.00 L solution …
8. ### Chemistry

A1g sample of enriched water, a mixture of H2O AND D2O, reacted completely with Cl2 to give a mixture of HCl and DCl. The HCl and DCl were then dissolved in pure H2O to make a 1.00 L solution. A 25.00 mL, sample of the 1 L solution …
9. ### Chemistry

A mixture of ethane and ethene occupied 35.5 L at 1.000 bar and 405 K. This mixture reacted completely with 110.3 g of O2 to produce CO2 and H2O. What was the composition of the original mixture?
10. ### Chemistry

An 0.850 g sample of a mixture of LiH and CaH2 was reacted with H2O and the H2 gas produced, 1.20 L, was collected at STP. What mass % of the original mixture was LiH?

More Similar Questions