Chemistry Unit 5: Chromium (III) solution reaction with ammonia (limited and excess)

Watch this thread
Ayman!
Badges: 15
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#1
Report Thread starter 6 years ago
#1
Hi, everyone! I have a Chemistry Unit 5 mock tomorrow, so would really appreciate help.

Upon adding limited NH3(aq):
\[[Cr(H_{2}O)_{6}]^{3+}_{(aq)} + 3NH_{3}_{(aq)} \rightarrow [Cr(H_{2}O)_{3}(OH)_{3}]_{(s)} + 3NH_{4}^{+}

Upon adding excess NH3(aq):
[Cr(H_{2}O)_{3}(OH)_{3}]_{(s)} + 6NH_{3}_{(aq)}\rightarrow [Cr(NH_{3})_{6}]^{3+}_{(aq)} + 6H_{2}O_{(l)}\]

Could anyone confirm if this equation is right?

Also, is the final solution green or purple? George Facer is saying green but my teacher said purple is safer to write. I've watched a YouTube video depicting a purple solution, though.
0
reply
RMNDK
Badges: 3
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#2
Report 6 years ago
#2
(Original post by aymanzayedmannan)
Hi, everyone! I have a Chemistry Unit 5 mock tomorrow, so would really appreciate help.

Upon adding limited NH3(aq):
\[[Cr(H_{2}O)_{6}]^{3+}_{(aq)} + 3NH_{3}_{(aq)} \rightarrow [Cr(H_{2}O)_{3}(OH)_{3}]_{(s)} + 3NH_{4}^{+}

Upon adding excess NH4(aq):
[Cr(H_{2}O)_{3}(OH)_{3}]_{(s)} + 6NH_{3}_{(aq)}\rightarrow [Cr(NH_{3})_{6}]^{3+}_{(aq)} + 6H_{2}O_{(l)}\]

Could anyone confirm if this equation is right?

Also, is the final solution green or purple? George Facer is saying green but my teacher said purple is safer to write. I've watched a YouTube video depicting a purple solution, though.
Actually, wait the second equation, I would advise rewriting from the start, i.e [Cr(H2O)6]3+ + 6NH3--> etc
In your equation, you'd need to add in the hydroxide ions.
The precipitate in the first equation is green but when it dissolves, the end solution is purple.
1
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Have you done work experience at school/college?

Yes (155)
41.67%
Not yet, but I will soon (69)
18.55%
No (148)
39.78%

Watched Threads

View All