Forum

Atoms and molecules

Which postulate of Dalton’s
atomic theory can explain the law
of definite proportions?

Atoms and molecules

Which postulate of Dalton’s
atomic theory is the result of the
law of conservation of mass?

Atoms and molecules

Hydrogen and oxygen combine in
the ratio of 1:8 by mass to form
water. What mass of oxygen gas
would be required to react
completely with 3 g of hydrogen
gas?

Atoms and molecules

In a reaction, 5.3 g of sodium
carbonate reacted with 6 g of
acetic acid. The products were
2.2 g of carbon dioxide, 0.9 g
water and 8.2 g of sodium acetat. Show that these observations are in agreement
with the law of conservation of
mass.
sodium carbonate + acetic acid
→ sodium acetate + carbon
dioxide + water

Is matter around us pure?

Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron

(c) Mixing of iron filings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of a candle

Is matter around us pure?

Classify the following into elements, compounds and mixtures.
(a) Sodium
(b) Soil
(c) Sugar solution
(d) Silver
(e) Calcium carbonate
(f) Tin
(g) Silicon
(h) Coal
(i) Air
(j) Soap
(k) Methane
(l) Carbon dioxide
(m) Blood

Is matter around us pure?

Which of the following will show “Tyndall effect”?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution

Is matter around us pure?

Identify the solutions among the following mixtures.
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water

Is matter around us pure?

Which of the following materials fall in the category of a
“pure substance”?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(i) Air

Is matter around us pure?

How would you confirm that a colourless liquid given to you is pure water?