NEED HELP are the counterfeit coins examples of mixtures, compounds, or elements?

Acompound has a molecular weight of 12.124 atomic mass units and the empirical formula c3h40. what is the molecular formula of the compound?

What is the mass of oxygen gas is consumed in a reaction that produces 4.60mol so2

The lattice enthalpy (formation of ionic solid from ions in the gas phase) for agcl(s) is -916 kj/mol and the hydration enthalpy (dissolution of gaseous ions into water) is -850 kj/mol. how much heat (in joules) is involved in forming 1l of saturated agcl solution (1.8 × 10-4 g / 100 ml water) by dissolving agcl(s)? assume solution volume does not change much upon dissolution. the equations are given below. ag+(g) + cl−(g) æ agcl(s)