Atomic Foundations of Matter
Class 9 · Science · 43 Questions
Water can be obtained from various sources. Are all these samples of water chemically identical?
Oxygen is sometimes represented as O and sometimes as O₂. What is the difference between these symbols?
Why does dissolved salt in water conduct electricity, but sugar does not?
Design and perform an experiment to test the hypothesis that mass is conserved during the chemical reaction. You may use a set-up different from the one shown in Activity 9.2.
A compound consists of 40% sulfur and 60% oxygen by mass. In a sample of the same compound containing 20 g of sulfur, what mass of oxygen must be present to satisfy the Law of Constant Proportions?
Carbon monoxide (CO) contains carbon and oxygen in the mass ratio of 3:4. How much oxygen will combine with 9 g of carbon to form carbon monoxide?
The Law of Definite Proportions holds true for compounds but not for mixtures. Give reason.
Students X and Y, both prepared an oxide of copper by combining copper and oxygen in the ratios of 4:1 and 8:2, respectively. Do their results justify the Law of Constant Proportions? Explain.
Assertion (A): 2 g of hydrogen combines with 16 g of oxygen to form 18 g of water. Reason (R): According to Dalton's Atomic Theory, atoms combine in a simple whole number ratio by mass to form compounds.
Nitrogen has five valence electrons. Draw the structure of the nitrogen molecule (N₂).
The atomic number of fluorine is 9. Explain the formation of the fluorine molecule (F₂).
What kind of ion will oxygen (O) form?
Fill in the blanks. Among magnesium and chlorine, magnesium atom can give two electrons to become Mg²⁺. However, chlorine can take only one electron to become _____. Now, _____ ion of magnesium and _____ ions of chlorine combine to give magnesium chloride.
Show the formation of cations of potassium (K) and calcium (Ca) atoms, and the formation of their corresponding chlorides using diagrams.
Illustrate how sodium sulfide (Na₂S) is formed.
Name the following: (i) CO₂ ___ (ii) NO₂ ___ (iii) SF₆ ___ (iv) PCl₃ ___
Write the formula for the following: (i) Sodium hydrogencarbonate ___ (ii) Sulfur dioxide ___ (iii) Ferric chloride ___ (iv) Cuprous oxide ___
Write the formulae for the compounds formed from the following pairs of ions: (i) Fe³⁺ and OH⁻ (ii) K⁺ and CO₃²⁻
Can you give a reason? (Covalent compounds such as camphor and naphthalene do not conduct electricity.)
Predict whether ionic and covalent compounds would conduct electricity in the molten state (the melted state of a substance).