Give me some extra questions of ch 3 chemistry class 9 out of ncert syllabus you may give it from any help book also!!

Give me some extra questions of ch 3 chemistry class 9 out of ncert sy

1.	Give me some extra questions of ch 3 chemistry class 9 out of ncert syllabus you may give it from any help book also!!
Answer» E solve this question Q: if the isotope of CHLORINE with masses 35 units is present 75% in nature and 37 units is present 25% in nature ,then find the average mass of the both isotopes of chlorine?