How do you convert?

Question

I have three questions from chemistry that I don't understand please help and can I get step-by-step work so I can understand how to do this for myself.

1. Convert 52.7 pints to cm3.

2. Convert 67.00 Mg to mg.

3. Convert 6.234 kcal to kj.

Answer 1

In general and introductory chemistry, they usually teach you, and want you to use, dimensional analysis.   You still need to know the conversion factors.  You multiply ratios so that you can cancel the units you don't want, and keep the units you do want.  Thus, in the problems you pose, you would set them up as follows:

 

1,  52.7 pints x 473 cm3/pint = answer (you need to know there are 473 cm3 in a pint). Note how pints cancel leaving cm3

2.  67.00 Mg x 106 mg/Mg = answer (again, you need to know conversion of mg to Mg.  Mg cancel leaving mg)

3.  6.234 kcal x 4.184 kJ/kcal = answer (same idea as above)

 

 

Answer 2

Hi Melonie from Campbell, CA...hope you are having a great weekend. 

Glad you contacted Wyzant...I am here to help.

 

Great conversion problems. I will help you with learning how to set them up and then work toward solving them.

Just a couple of things when we solve them. We set them up as a ratio, comparing one thing to another. One of those things you need to understand as the top and bottom values represent the same thing.

Here are two example[sorry if I use Sunday football as an example]

        1 touchdown is the same as 6 points, in a ratio you can write that as

 

        1 touchdown   

          6 points

 

Another example is 1 year is the same as 365 days[except for Leap Years]

so you can write:

               1 year               and so if a problem is to find out how many

             365 days             days are in 5 years, you set up you equation

 

              1  year         =        5 years      excluding Leap Years for this

            365 days                   x days                        example

 

Remember that part in math when you have ratios, you can do something

 called 'cross multiply'? You do that here. Rewrite the ratios like this:

 

    (1 year)(x days) = (365 days)(5 years)    Now you work to solve the

                                                                  operations...multiply

    (1 year)(x days)  =  (1825 days•years)    Now your next step is to

                                                                 eliminate years, this is how

  (1 year)(x days)  =   (1825 days•years)     Divide by years and cancel

         years                         years

 

               x days   =    1,825 days             You are left with 1,825 days

                                                                    in 5 years.

 

  With this understanding your next step is to find out, this is probably in your textbook or you will need to research these 3 equivalents:

 

How many cubic centimeters (cm³) in one pint: then set up your equation

 

                             1 pint     =     52.7 pints    

that goes here  ⇒   x cm³              x cm³       then complete the operation

 

the second problem is confusing...is this written correctly. The way I read the problem is 'Convert 67.00 Magnesium to milligrams' is that right?

 

And the last problems...Convert 6.234 kcals to kilojoules...Right?

Find out how many kcals(kilocalories) are in one kj?

                              1 kcal          =         6.234 kcal     

that goes here ⇒       x kj                          x kj 

 

Now you have all the tools to solve these kind of problems. Check to see about the second problem...it is confusing.

 

I hope this helps you understand what it is that you needed help with.

If you need any further help...contact me on Wyzant.