What you have to do is find a periodic table and add the mass of each atom that the compound is made of.
Ca= 40.1
O= 16.0
H= 1.01
keep in mind that you have to also account for how many atoms of each there are in the molecule. for example, in Ca(OH)2, there are one Ca, two O and two H
so the molar mass of Ca(OH)2= 40.1 + (2 x 16.0) + (2 x 1.01)= 74.12 g/mol
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Answer:
54.1 % Ca, 43.2 % O, 2.7% H
Explanation:
Molecular formula for calcium hydroxide is Ca(OH)₂
As we don't have a mass of Ca(OH)₂ to find out the percentage composition, we consider that the question refers to 1 mol of compound.
1 mol of hydroxide weighs 74.08 g
1 mol of hydroxide has 1 mol of Ca, therefore 40.08 g are Ca
2 moles of O therefore 32g are O
2 moles of H therefore 2 g are H
Percentage composition is known as (Mass of element/Total mass) . 100
(40.08 / 74.08) . 100 = 54.1 %
(32 / 74.08) . 100 = 43.2 %
(2 / 74.08) . 100 = 2.7%
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Answer: The temperature of the gas reduced to 400K.
Explanation:
Stated that ; The pressure remains the same, that is initial and final pressure equals 1atm.
Applying Charles Law

Initial volume V1 = 1
Final volume V2 = 1/2 (halved)
Initial temperature T1 =800K
Final temperature T2 = ?
(1/800) = (1/2)/T2
T2 = 800/2
T= 400K
Therefore, when the volume is halved, the temperature reduced also to half ( 400K)
Answer:
69.8 kilo Pasacl is the pressure of the hydrogen gas.
Explanation:

Pressure at which hydrogen gas collected = p = 101.2 kilo Pascals
Vapor pressure water =
= 31.4 kilo Pascals
The pressure of hydrogen gas = P
The pressure at which gas was collected was sum of vapor pressure of water and hydrogen gas.


69.8 kilo Pasacl is the pressure of the hydrogen gas.