Aluminium trichloride (
) is an ionic substance that forms crystals in the solid phase. Water molecules may be trapped inside the crystal lattice. We represent this as:
. A learner heated some aluminium trichloride crystals until all the water had evaporated and found that the mass after heating was
. The mass before heating was
. What is the number of moles of water molecules in the aluminium trichloride?
We first need to find n, the number of water molecules that are present in the crystal. To do this we first note that the mass of water lost is
.
The next step is to work out the mass ratio of aluminium trichloride to water and the mole ratio. The mass ratio is:
To work out the mole ratio we divide the mass ratio by the molecular mass of each species:
Next we do the following:
and
So the mole ratio of aluminium trichloride to water is:
And now we know that there are 6 moles of water molecules in the crystal.
Khan academy video on molecular and empirical formulae - 1
Khan academy video on mass composition - 1
Moles and empirical formulae
Calcium chloride is produced as the product of a chemical reaction.
What is the formula of calcium chloride?
What percentage does each of the elements contribute to the mass of a molecule of calcium chloride?
If the sample contains
of calcium chloride, what is the mass of calcium in the sample?
How many moles of calcium chloride are in the sample?
of zinc combines with
of sulphur. What is the empirical formula of zinc sulphide?
What mass of zinc sulphide will be produced?
What percentage does each of the elements in zinc sulphide contribute to its mass?
Determine the formula of zinc sulphide.
A calcium mineral consisted of 29,4% calcium, 23,5% sulphur and 47,1% oxygen by mass. Calculate the empirical formula of the mineral.
A chlorinated hydrocarbon compound was analysed and found to consist of 24,24% carbon, 4,04% hydrogen and 71,72% chlorine. From another experiment the molecular mass was found to be
. Deduce the empirical and molecular formula.
Molar volumes of gases
It is possible to calculate the volume of one mole of gas at STP using what we know about gases.
Write down the ideal gas equation
, therefore
Record the values that you know, making sure that they are in SI units You know that the gas is under STP conditions. These are as follows:
Substitute these values into the original equation.
Calculate the volume of
of gas under these conditions The volume of
of gas at STP is
.
The standard units used for this equation are
in
,
in
and
in
. Remember also that
and
.
A sample of gas occupies a volume of
, has a temperature of
and has a pressure of
. Calculate the number of moles of gas that are present in the sample.
The only value that is not in SI units is volume.
.
We know that
Therefore,
Questions & Answers
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
