Practice Worksheet
CBSE Class 9 Science
Topic: Atoms and Molecules
Very Short Answer
Q1) Sample A contains one-gram molecules of oxygen molecules and sample B contains one mole of oxygen molecules. What is the ratio of the number of molecules in both the sample?
Ans: One gram molecules and one gram mole contain the same number of molecules ( 6.022 x 1023).Therefore, the ratio is 1:1
Q2) An element X has valency 3 while the element Y has valency 2. Write the formula of the compound between X and Y.
Ans: X2Y3
Q3) Identify the cations and anions in the following compound.
NH4Cl
Ans: NH4+, Cl-
Q4) An element X exhibits variable valencies 3 and 5. Write the formulae of the chlorides of the element.
Ans: XCl5 and XCl3
Q5) Give an example of trivalent cation and monovalent anion.
Ans: Trivalent cation Al3+, monovalent anion Cl-
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