The problem states, 'A student wants to determine how long it takes to dissolve 51.3 g of common table salt (sodium chloride) in 1L of water by monitoring the solution. It takes 26.7 seconds for the salt to completely dissolve. Determine the rate of dissolution and describe the rate constant expression if the reaction was first-order in NaCl.'

For the first bit, I multiplied the mass by the molar mass of NaCl to get about 0.878 moles and then divided that by the time to get about 0.0329 mol/s. Does that sound about right?

For the second bit, do they just want me to say rate=k[NaCl]?

Thanks!

A couple of points here. First, mol = grams/molar mass and not what you have. Then mols/L/s will give you about 0.0344 M/s and not mols/s.

Yes, your calculation for the rate of dissolution seems correct. To determine the rate, you divided the number of moles of NaCl (0.878 mol) by the time taken (26.7 seconds), resulting in approximately 0.0329 mol/s.

For the second part, yes, the rate constant expression would be written as rate = k[NaCl]. This indicates that the rate of dissolution is directly proportional to the concentration of NaCl, which signifies a first-order reaction with respect to NaCl.

Yes, you are correct for the first part of the question. To determine the rate of dissolution, you need to convert the mass of NaCl to moles by multiplying it by the molar mass of NaCl. So multiplying 51.3 g by the molar mass of NaCl (58.44 g/mol) gives you approximately 0.878 moles. Then, dividing this number by the time taken (26.7 seconds) gives you a rate of approximately 0.0329 mol/s.

For the second part of the question, you are on the right track. If the reaction is first-order in NaCl, the rate constant expression can be written as rate = k[NaCl]. This means that the rate of dissolution is directly proportional to the concentration of NaCl, with the rate constant (k) determining the specific rate at which the reaction proceeds. By knowing the rate constant expression, you can relate the rate of dissolution to the concentration of NaCl.