Question

1a. You have 2.32 x 1024 molecules of water, H2O. How many moles of water is this ?

a. 18.02 moles b. 3.85 moles c. 6.022 x 1023 moles d. 4.18 x 1025 moles

1b. How many grams of water are in the sample described in part “a” ?

a. 18.02 grams b. 2.32 grams c. 69.4 grams d. 6.022 grams

1c. How many hydrogen atoms are the sample described in part “a”?

a. 2 b. 2.32 x 1024 c. 4.64 x 1024 d. 6.022 x 1023 2.

Avogadro's number of magnesium atoms….

a. has a mass of 1.00 gram

b. weighs the same as Avogadro’s number of sulfur atoms

c. has a mass of 12.00 grams

d. is one mole of magnesium

e. has a mass of 6.022 x 1023 grams

Answer 1

Solution--

1.a

Given,

2.32* 10^24 molecules of H2O

We know that, 6.022 *10^23 molecules of water in 1 mole

Therefore, 2.32 * 10^24 molecules of water

=( 2.32 * 10^24 * 1 mole ) / 6.022 * 10^23 = 3.85 mole of H2O

Hence the option (b) is correct.

1.b

We know that,

Mass of 1 mole H2O = 18 g/mole

Therefore,

3.85 mole of H2O = 18 g/ mole * 3.85 mole = 69.3 g

Hence ,the option (c) is correct.

1.c

The number of hydrogen atoms in 1 mole = 6.022*10^23

Therefore, the number of hydrogen atoms in 3.85 mole =( 6.022 * 10^23 )* 3.85 mole = 2.32 * 10^ 24 .

Hence, the option (b) is correct.