Question

How many moles of solute are present in the following solutions? 175 mL of 0.36 M NaNO3 Express your answer using two significant figures. 460 mL of 1.4 M HNO3 Express your answer using two significant figures.

Answer 1

We have few data given which can be noted first.

Solution 1- Molarity = 0.36 M

Volume = 175 mL

we need to convert volume in litres as Molarity is defined as number of moles of solute per litre of the solution

thus, volume of solution = 175 mL = L (as 1 L = 1000 mL)

volume of solution = 0.175 L

Now, Molarity of solution = number of moles of solute/ volume of solution in litres

0.36 = number of moles of solute/ 0.175

number of moles of solute = 0.36 x 0.175 = 0.063 moles of solute.

Thus, number of moles in solute of 175 mL of 0.36M NaNO₃ solution is 0.063 moles or 6.3 x 10^-2(in terms of two significant figures).

Solved.

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Solution 2-   Molarity = 1.4 M

Volume = 460 mL

we need to convert volume in litres as Molarity is defined as number of moles of solute per litre of the solution

thus, volume of solution = 460 mL = L (as 1 L = 1000 mL)

volume of solution = 0.460 L

Now, Molarity of solution = number of moles of solute/ volume of solution in litres

1.4 = number of moles of solute/0.460

number of moles of solute =1.4 x 0.460 = 0.644 moles of solute.

Thus, number of moles in solute of 460 mL of 1.4M HNO₃ solution is 0.64 moles or 6.4 x 10^-1(in terms of two significant figures).

Solved.