Question

Part A

Answer 1

Answer

mass of 1 mole = 18g

mass of 1 mL = 1g

the unit used is gram

Explanation:

There are two ways to find mass of water:

1st way:

If we find Mass of water for one mole of water:

For this purpose we use mole formula as below

                          no. of moles = mass in grams / molar mass

if we find mass for one mole of water:

then

no. of moles of water = 1 mol

molar mass of water = H₂O = (1x2 +1x16) = 18 g/mol

mass of water = ?

Put the value in the mole formula

          no. of moles = mass in grams / molar mass . . . . . . . . . . . . (1)

by rearranging the formula (1)

            mass in grams = no. of moles x molar mass

            mass in grams = 1 mole x 18 g/mol

            mass in grams =  18 g

So for one mole of water the mass of water is 18 g and the unit for it is gram.

2nd way:

We can find mass of water by another way too

if we find the mass 1 mL of water

then the formula will be used is

                              D = m/v

where D is density

m is the mass

and v is the volume

So

density of water for 1 mL (D) = 1 g/ml

volume of water = 1 mL

mass of water = ?

By Rearranging density formula for mass

                                m = D/v ......................... (2)

put the values in equation 2

                                m= 1gmL⁻¹ / 1 mL

                                 m= 1g

So the mass of 1mL is 1g