James needs 4.20 moles of nabr for an experiment. how many grams of nabr must he measure out to have 4.20 moles?

Ans: Mass of NaBr = 432 g

Given:

# moles of NaBr = 4.20 moles

To determine:

The mass corresponding to 4.20 moles of NaBr

Explanation:

The # moles of a given substance is the ratio of its mass to molar mass

moles = mass (g)/molar mass (g.mol-1)(1)

Molar mass of NaBr = 102.89 g/mol

Based on equation(1)

mass = moles * molar mass

        = 4.20 moles * 102.89 g.mol-1 = 432 g

1.43 x 10^-11 j the guy commented the awnser just making sure u see it .

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.