Question

I don’t understand this please help!!!

Answer 1

Answer:

Numbers after atoms are subscripts. Numbers before atoms are coefficients.

Equation: 2Na +Cl2 -> 2NaCl

Given: 6.8 grams of Na  

Unknown: moles of NaCl

Set up: $6.8g Na *\frac{1 mole Na}{22.99 g Na}*\frac{2 moles NaCl}{2 moles Na} =.2957 moles NaCl$

Explanation:

We know that the reactants are Na and Cl and that what is being produced, the products, is NaCl.

Na + Cl -> NaCl

CAREFUL! Cl is a diatomic ion, is it gets a subscript of 2! This means there need to be 2 cl atoms on the right side as well. But now there are 2 Na on the right side. So we multiply Na by 2 on the left so that both sides have two Na atoms.

2Na +Cl2 -> 2NaCl

B)

We know that there are 6.8 grams of Na. This is our given.

What do we want to find out? We want to find how many moles of NaCl there are, so that is our unknown.

C) A mole ratio is exactly what it sounds like. From our balanced equation, we can see that there are 2 moles of Na  and 2 moles of NaCl. In other words, there are 2 moles of Na for every 2 moles Nacl. In notation, this is $\frac{2 mole Na}{2 Mole NaCl}$ or 2:2. You can simplify to 1:1 ratio, but as equations get more complex I find it easier to not. It depends on what your teacher wants and what you find easier.  

D)

By set up I assume they mean stoichiometry (chemistry conversion) . First I'm going to split up the set up so that it is easier to understand.

We start with the given and convert that into moles Na. We can do this by remembering that there are 22.99 grams for every 1 mole Na:

6.8 g Na* $\frac{1 mole Na}{22.99g Na} = .2957 moles Na$

Now we can use that mole ration we found in part C to convert moles of Na into moles of NaCl:

$.2957 moles Na *\frac{2 moles NaCl}{2 moles Na}= .2957$

Usually, we will put these together to get

$6.8g Na *\frac{1 mole Na}{22.99 g Na}*\frac{2 moles NaCl}{2 moles Na} =.2957 moles NaCl$

Tip: in Stoichiometry, it is important to remember that your units should cancel out until you only have the units you want. If there are moles of Na in the numerator, there should be moles of Na in the denominator of the following fraction. If there are grams Na in the numerator, there should be grams Na in the denominator and so and so on until you are only left with the unit you want, which, in this case, is moles of NaCl.