The correct answer is (b) Elements are always present in a fixed proportion by mass in a chemical compound. The Law of Constant Proportion, proposed by Joseph Proust, states that a chemical compound always contains the same elements in the ...
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The correct answer is (d) Ca₃(PO₄)₂. Calcium phosphate is composed of three calcium (Ca²⁺) ions and two phosphate (PO₄³⁻) ions, forming the chemical formula Ca₃(PO₄)₂. It is an important component of bones and teeth. Class 9th Science NCERT MCQ Questions
The correct answer is (c) (i) and (iv). Alloys are mixtures of two metals (e.g., brass – copper and zinc) or a metal and mercury (called an amalgam, e.g., silver amalgam used in dental fillings). Non-metals generally do not form ...
The correct answer is (b) Sulphur in CS₂. Sulfur dissolves completely in carbon disulfide (CS₂) to form a true solution, not a colloid. In contrast, starch in water, soap solution, and petrol in CS₂ form colloidal dispersions. Class 9th Science ...
During a chemical change, both the chemical and physical properties of a substance change (c). The composition of the substance is altered, forming a new substance with different properties, such as color change, gas formation, or energy release in the ...