134. how many of the following statements are true concerning chemical equations? i. coefficients can be fractions. ii. subscripts can be fractions. iii. coefficients represent the relative masses of the reactants and/or products. iv. changing the subscripts to balance an equation can be done only once. v. atoms are conserved when balancing chemical equations.

Statements I and V are true

Explanation:

I. Coefficients can be fractions. (TRUE)

Let's suppose we have the following reaction:

Fe + O₂ > Fe₂O₃

This can be balanced with round numbers like these:

4Fe + 3O₂ >2Fe₂O₃

But if we use simplification of these numbers, dividing by 2 the whole equation we have the following:

2Fe + 3/2O₂ > Fe₂O₃

The fraction 3/3 is multiplied by the 2 of the molecule of oxygen: 3/2 * 2 = 3, and with this we'll have the same atoms of oxygen on both sides of equations. Therefore, we can use fractions as coefficients.

II. Subscripts can be fractions. (FALSE)

Subscripts in a chemical reactions represents atoms and these cannot be fractions cause atoms are not represented in a chemical equation with fractions, for example:

Fe + O₂ > FeO

We cannot write to balance the equation something like this:

Fe + O1/2 > FeO1/2,

The numbers that we use to balance are always written behind the molecules a s coefficients, that's why subscripts are not fractions.

III. Coefficients represent the relative masses of the reactants and/or products. (FALSE)

This is not true either, because the coefficients in a chemical reactions always represent moles of the molecules, and then, with stechiometry we can have an idea of how many moles can be produced in one reaction.

IV. Changing the subscripts to balance an equation can be done only once.  (FALSE)

Subscripts represent the atoms of a element or compound as they are in their natural state, so these cannot be changed to balance a equation, we can only use numbers as coefficients and these numbers can be changed.

V. Atoms are conserved when balancing chemical equations. (TRUE)

As we stated in the above four statements, the atoms are conserved basically because the only numbers changing in a chemical equation are the coefficients, therefore, the original atoms in reactions are conserved.

i believe it is 40–40–20%

explanation:

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6