Question

Europium can have a 2+ or a 3+ charge. Which one of the formulas is not possible? 1) EuSO4 2)Eu2(SO4)3 3 EuPO4 4)Eu(NO3)3 5) EuHCO3

Answer 1

5) `"EuHCO"_3` is not possible.

Explanation:

We can calculate the charge on `"Eu"` in each compound.

1) `"EuSO"_4`

`stackrelcolor(blue)("+2")("Eu")stackrelcolor(blue)("-2")("SO"_4)`

`"SO"_4"` has a charge of 2-, so `"Eu"` must have a charge of 2+.

2) `"Eu"_2("SO"_4)_3`

`stackrelcolor(blue)("+3")("Eu")_2stackrelcolor(blue)("-2")(("SO"_4)_3`

The three `"SO"_4^"2-"` ions have a total charge of 6-, so the two `"Eu"` ions must have a total charge of 6+.

One `"Eu"` ion must have a charge of 3+.

3) `"Eu""PO"_4`

`stackrelcolor(blue)("+3")("Eu")stackrelcolor(blue)("-3")("PO"_4)`

`"PO"_4"` has a charge of 3-, so `"Eu"` must have a charge of 3+.

4) `"Eu""(NO"_3)_3`

`stackrelcolor(blue)("+3")("Eu")stackrelcolor(blue)("-1")(("NO"_3))_3`

The three `"NO"_3"` ions have a total charge of 3-, so the `"Eu"` ion must have a charge of 3+.

One `"Eu"` ion must have a charge of 3+.

5) `"Eu""HCO"_3`

`stackrelcolor(blue)("+1")("Eu")stackrelcolor(blue)("-1")("HCO"_3)`

`"HCO"_3"` has a charge of 1-, so `"Eu"` must have a charge of 1+.

A charge of 1+ on `"Eu"` is not allowed.

The correct formulas are `"Eu"("HCO"_3)_2` and `"Eu"("HCO"_3)_3`