A mole refers to <span>6.022⋅<span>1023</span></span> items. <span><span>H2</span>O</span> has 2 hydrogen atoms and 1 oxygen atom...so a total of 3 atoms in each <span><span>H2</span>O</span>.
Therefore <span><span>(6.022⋅<span>1023</span>)</span>⋅</span> (3 atoms) <span>=18.066⋅<span>1023</span></span>
Then we need to change the answer into proper scientific notation:
<span>18.066⋅<span>1023</span>=1.8066⋅<span>1024</span></span>
Lastly, change to the proper number of significant figures. There are 4 significant figures in 6.022. Due to this we need to also have 4 significant figures in the final answer, so we would round <span>1.8066⋅<span>1024</span>→1.807⋅<span>1024</span></span>
So, your final answer is <span>1.807⋅<span>10<span>24 for one mole of h2o. multiply that by 7 and your answer is 13.55 * 1024 </span></span></span>
