Elements, Compounds and Equations

Elements, compounds, mixtures and chemical equations.

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Q1 · Elements, Compounds and Equations · EASY
A student mixed sand and salt in water. After stirring, the salt dissolved but the sand settled at the bottom. What type of matter is this sand-salt-water combination?
Q2 · Elements, Compounds and Equations · MEDIUM
When magnesium ribbon burns in air, it forms magnesium oxide. If 24 g of magnesium reacts completely with 16 g of oxygen, how much magnesium oxide is formed?
Q3 · Elements, Compounds and Equations · MEDIUM
Which of the following statements correctly distinguishes a compound from a mixture?
Q4 · Elements, Compounds and Equations · HARD
Consider the chemical equation: Fe + CuSO4 → FeSO4 + Cu. A teacher wants to demonstrate this reaction to show the reactivity of metals. What does this equation tell us about the reactivity of iron compared to copper?
Q5 · Elements, Compounds and Equations · HARD
What is the percentage of oxygen in calcium carbonate (CaCO₃)? (Atomic masses: Ca = 40, C = 12, O = 16)