How would you test your gold jewelry to determine whether it is a pure compound or a mixture?

Calculate the density of the ring by dividing the mass in grams by the volume in milliliters. Compare this number to the standard density of gold, which is 19.32 grams per milliliter. If your calculated density is very close to the standard density, you can be confident that your ring is pure gold.

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the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.