Question

An aqueous solution of sodium

Answer 1

Answer:

2.5×10^-7mol/dm^3

Explanation:

Firstly convert the cm^3 to dm^3

200×1000=200000dm^3

Calculate the g/dm^3

2/200000=0.00001g/dm^3

To calculate mol/dm^3

Mol/dm^3=mass given\molar mass

=0.00001/40

=2.5×10^-7mol/dm^3

Answer 2

Answer:

0.25mol/dm^3

Explanation:

Let us calculate the number of mole in 2g of NaOH. This is illustrated below:

Molar Mass of NaOH = 23 + 16 + 1 = 40g/mol

Mass of NaOH given = 2g

Number of mole = Mass /Molar Mass

Number of mole of NaOH = 2/40 = 0.05mole

Volume = 200cm^3

1000cm^3 = 1dm^3

200cm^3 = 200/1000 = 0.2dm^3

Molarity = mole/Volume

Molarity = 0.05/0.2

Molarity = 0.25mol/dm^3