Need help with chemistry conversion factors

Nurses General Nursing

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I'm taking chemistry 115, and need some help on this question.

The daily dose of ampicillin for the treatment of an ear infection is 115mg ampicillin per kilogram of body weight (115mg/kg), What is the daily dose for a 27lb child?

So far I've done this, but am not sure if its the right answer. And significant figures matter.

27lb x 1kg = 12kg x 115mg = 1380 mg

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2.20lb

I set it up in a conversion factor, that 1kg equals 2.20lbs, and the lbs symbols cancel each other out, so I end up taking 27 divided by 2.20 and I get 12 kg and since its 115mg per every kg I took 12kg multiple 115mg and got 1380 mg as the dose for a 27lb child.

I need to remember to use significant figures too ....Am I right???

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Specializes in Med/Surg, Ortho, ASC.

Have you tried posting this question on the student nurse forum?

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Specializes in ER, CCU, Admin, Transplant.

I believe it would be to convert lbs to kgs...27 lbs divided by 2.2=12.3 kgs (rounded)

12.3 kgs x 115 mg (per kg ) = 1415 mg. ( rounded)

Hope this helps.

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Specializes in Utilization Management.

With kids or anyone under 100lbs, you round to the hundredths place with weight...so 27lbs would equal 12.27kg...12.27kg x 115mg = 1411.05mg or 1411mg/day...but I'm sure rounding rules vary with schools.

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With kids or anyone under 100lbs you round to the hundredths place with weight...so 27lbs would equal 12.27kg...12.27kg x 115mg = 1411.05mg or 1411mg/day...but I'm sure rounding rules vary with schools.[/quote']

Yes, that is the same thing that I came up with (1411mg/day). The key is to make sure you round your significant figures after you do your math (the answer). If you round beforehand your answer can be off.

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Specializes in med/surg, telemetry, IV therapy, mgmt.

the daily dose of ampicillin for the treatment of an ear infection is 115mg ampicillin per kilogram of body weight (115mg/kg), what is the daily dose for a 27lb child?

115 mg/kg
(dose desired)
x 27 pounds/1
(weight of child)
x 1 kg/2.2 pound
(conversion factor)
= 1411.363636 mg,
rounded to
1411.4 mg
(daily dose)

i did this by dimensional analysis and came up with different math than you did.

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