Suppose that 2.50 g of NaCl (molar mass = 58.5 g/mol) is required for a certain reaction. If the NaCl is available as a 0.150 M solution, now many mL of the solution must be used?
a. 375 mL
b. 285 mL
c. 43.1 mL
d. 16.7 mL
e. 13.3 mL
I cannot figure this questions out! Please help it's killing me!!!
Thankyou! xx
a. 375 mL
b. 285 mL
c. 43.1 mL
d. 16.7 mL
e. 13.3 mL
I cannot figure this questions out! Please help it's killing me!!!
Thankyou! xx
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Ok i can help you out with this problem.
the formula you want here is M = m/v. Where M stands for molarity, m = moles, and v = volume.
Whenever you have grams and a molar mass, you'll usually want to convert to moles. so lets start with that.
To convert to moles you take the grams of NaCl 2.50 and divide by the molar mass.
the setup looks something like this:
2.50g NaCl x 1 mole NaCl / 58.5 g NaCl. Notice the units here, the grams cancel out, and you are left with moles. your answer 0.0427 moles of NaCl.
Now you have a Molarity, and moles so use these values to find how many liters you will obtain.
M = m/v
0.150M = 0.0427moles/ v . cross multiplying you get 0.150M v = 0.0427moles
divide by 0.150 and you get 0.285 Liters. whenever you have Molarity, and moles, it is important to note that volume is measured in liters with this equation, so since the choices are in mL, you'll have to convert by multiplying .285 liters x 1000, and you obtain 285ml. so thats your answer
the formula you want here is M = m/v. Where M stands for molarity, m = moles, and v = volume.
Whenever you have grams and a molar mass, you'll usually want to convert to moles. so lets start with that.
To convert to moles you take the grams of NaCl 2.50 and divide by the molar mass.
the setup looks something like this:
2.50g NaCl x 1 mole NaCl / 58.5 g NaCl. Notice the units here, the grams cancel out, and you are left with moles. your answer 0.0427 moles of NaCl.
Now you have a Molarity, and moles so use these values to find how many liters you will obtain.
M = m/v
0.150M = 0.0427moles/ v . cross multiplying you get 0.150M v = 0.0427moles
divide by 0.150 and you get 0.285 Liters. whenever you have Molarity, and moles, it is important to note that volume is measured in liters with this equation, so since the choices are in mL, you'll have to convert by multiplying .285 liters x 1000, and you obtain 285ml. so thats your answer
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Molarity = moles of solute / Liters of solution
Where molarity = 0.150 M
Liters of solution of what you are trying to solve for, and the moles of solute can be found by dividing the given mass by the molar mass of NaCl. Moles = 2.50 g / (58.4430 g/mol) = 0.04278
Thus, liters of solution = 0.04278/0.150 = 0.285
Convert this to mL by multiplying it by 1000.
Answer: 285 mL which is (b)
Where molarity = 0.150 M
Liters of solution of what you are trying to solve for, and the moles of solute can be found by dividing the given mass by the molar mass of NaCl. Moles = 2.50 g / (58.4430 g/mol) = 0.04278
Thus, liters of solution = 0.04278/0.150 = 0.285
Convert this to mL by multiplying it by 1000.
Answer: 285 mL which is (b)