# CHEM

for eg:
why is the oxidation state (#) of Ca in CaH2 "+2"? According to a p.table I have here +2 is the only oxidation # for Ca...but how is that figured?
One other eg:
the oxidation state (#) of the maganese atom in KMnO4.6H2O is "+7". How is this so & not: 2,3,or4?

If you assign charges to oxygen, it's (-2). There are 4 of these in the molecule. So 4*(-2) = -8. potassium is a +1 charge. So now you have (-8) +1 = (-7). Therefore, since there's only one Mn, that one atom is a +7 charge so that the -7 is balanced out to be neutral (since it's not an ion).

I hope this helps.. Just assign the charges for what you know, then calculate based upon the overall charge and the amount of that element in the molecule.

For the Ca ion, it is in group IIA (or 2 depending upon the system you are using). Alkali metals (group IA) and alkaline earth metals (IIA) are assigned oxidation states of +1 and {2 respectively. The other way you can do it is to know that hydrogen, in hydrides, (and this is a hydride) is
-1. Since there are two of them it makes the charge on H -2 for two H atoms; therefore, Ca must be +2 for the compound of CaH2 to be neutral.

1. 👍 0
2. 👎 0
3. 👁 82

## Similar Questions

1. ### Honors Chemistry

I have to fill in the blanks of these questions with the elements H (hydrogen), Co (cobalt), Ga (gallium), and O (oxygen), but different sources are telling me different things: 7. Its most common oxidation state is -2 8. A metal

asked by Emily (different from one before me) on September 28, 2009
2. ### Chemistry

Trying to name this compound and figure out its oxidation state [ CoBr2(NH3)3(H2O) ]+ I came up with triammineaquadibromocobalt(II) ion with a +3 oxidation state...but not sure if this is right... similarily for [Fe(ox)(Cl)4]3- I

asked by Trixie on April 7, 2010
3. ### Chem Oxidation-Reduction Titrations

H2O2→ O2 + 2H+ + 2e- OCl- + 2H+ + 2e-→ H2O+ Cl- H2O2(aq) + OCl-(aq) → H2O(l) + Cl- (aq) + O2(g)Assign oxidation numbers to the following atoms: O in H2O2 ________; Cl in OCl- __________The oxidizing agent for this RedOx rxn

asked by B on February 8, 2018
4. ### CHEM

What is the exact method/formula used to calculate oxidation state #'s? & how does one know when to use the correct oxidation state #? For example: Carbon carries 4,2,-4; Cl= 1,5,7,-1; and, Mn=2,3,4,7. Thanx. You use the seven

asked by K on December 14, 2006
5. ### Chemistry

Oxidation State numbers For Fe3+ i got 3+ b/c Oxidation state monatomic ion = ionic charge and i got that answer wrong. i am receiving wrong answers for these below aswell. I used these rules for the following -Alkali metals are

asked by Jerry on October 5, 2010
6. ### chemistry

Assign an oxidation state to each atom in each of the following compounds. 1) Fe(CN)3 i know Fe= +3 but how do i find the oxidation state for C and N? does CN have a normal over all charge?

asked by Samantha on May 5, 2011
7. ### chemistry

For the reaction, shown below, determine which statements are True and which are False. 3Fe(s) + Cr2O72-(aq) +14H+(aq) → 3Fe2+(aq) + 2Cr3+(aq) + 7H2O(l) ξo=1.77V 1. The oxidizing agent is dichromate (Cr2O72-). 2. The iron

asked by bekah on May 2, 2014
8. ### Chemistry

Balance the reaction of plumbate ions and hydrochlorite ions: Pb(OH)42-(aq) + ClO-(aq) → PbO2(s) + Cl- I put: Pb(OH)3-(aq) + ClO-(aq) → PbO2(s) + Cl-(aq) + H2O(l) + OH-(aq) It said: The reaction described in your answer is not

asked by Sara on June 21, 2013
9. ### Chemistry

Can someone check my answers? What is the oxidation state of each element in K2Cr2O7? K +1 Cr +6 O -2 What is the oxidation state of each element in SO32–? S +4 O -6

asked by Anon on December 2, 2012
10. ### chemistry

Following oxidation-reduction reaction by using the oxidation state method a) O2+H2O+Pb=Pb(OH)2

asked by mathew on October 5, 2014

More Similar Questions