How do you find the number of isotopes in an element?

Match the mixture with the substance// i really need on this guys (it’s a pic btw)

Effect of rotenone and antimycin a on electron transfer rotenone, a toxic natural product from plants, strongly inhibits nadh dehydrogenase of insect and fish mitochondria. antimycin a, a toxic antibiotic, strongly inhibits the oxidation of ubiquinol. (a) explain why rotenone ingestion is lethal to some insect and fish species. (b) explain why antimycin a is a poison. (c) given that rotenone and antimycin a are equally effective in blocking their respective sites in the electron-transfer chain, which would be a more potent poison? explain.

Calculate the number of kilojoules to warm 125 g of iron from 23.5°c to 78.0°c.