A gas exerts pressure on its container because?
the molecules of a gas collide with the walls of the container
some of the molecules are moving faster than others
of the collisions of the molecules with each other
of the mass of the molecules of the gas
Correct answer is A
Gas pressure is the name given to the force exerted by gas particles colliding with the wall of their container.
224cm3
168cm3
112cm3
100cm3
Correct answer is B
1mole of gas at STP = 22.4dm\(^3\)
0.0075 mole of CaCO3 = xdm\(^3\)
cross multiply;
where 22.4dm\(^3\) = 22400cm\(^3\)
x * 1 = 0.0075 * 22400 → 168cm\(^3\)
the gas CO2 which evolved was gotten from CaCO3 so we use the number of moles of CaCO3 only
33%
44%
55%
87%
Correct answer is B
molar mass of water [7H\(_2\)O] = 7[ 2 * 1 + 16] → 7 * 18 = 126g/mol
molar mass of ZnSO\(_4\).7H\(_2\)O = [65 * 1] + [32 * 1] + [16 * 4] + 7[ 2 * 1 + 16]
→ 65 + 32 + 64 + 126 = 287g/mol
percentage of water of crystallization = \(\frac{mass of water of crystallization}{mass of hydrated compound} * 100%\)
→ \(\frac{126}{287} * 100\) = 43.9
≈ 44%
Which of the following is a physical change?
Freezing ice cream
dissolving calcium in water
burning kerosene
Exposing white phosphorus to air
Correct answer is A
Freezing is a physical change. It involves a liquid changing states to a solid. Thus, freezing a substance will not change its chemical identity, but its state.
A mixture of sugar and sulphur can be separated by?
dissolution in water, evapouration and filtration
filtration, evaporation and dissolution in water
dissolution in water, filtration and evaporation
evaporation, dissolution in water and filtration
Correct answer is C
Sulfur is insoluble in water but sugar is soluble.
Hence; dissolution of sugar to have sulfur as the only insoluble solid.
Filtration: The filtrate is the liquid that passes through the filtration filter. Meanwhile, the residue is the solid that remains on the filtration filter.
Evaporation: water as part of the filtrate changes into a gas to leave sugar as residue.