Question about Texas Instruments BA-II Plus Calculator

# How do i enter a negative log - Texas Instruments BA-II Plus Calculator

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Type in the log, then use the change sign key (-) or (+/-) to negate the value displayed. You can also type in 0-log(x)

Posted on Jan 21, 2013

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Posted on Jan 02, 2017

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## Related Questions:

### How to fix error mesage on TI-30Xa. Every time I press LOG an error sign comes up. how do i fix this?

To take the log of a number, enter the number then press the LOG button, then the =. To take the log of a negative number, enter the negative number using the +/- key just to the right of the decimal point. To calculate the negative of a log, calculate the log and then negate it using +/-. To calculate the antilog (inverse logarithm), press 2nd then LOG.

Bear in mind that LOG is the common (base-10) logarithm. For the natural (base-e) logarithm, use the LN key to its right.

Nov 07, 2011 | Texas Instruments TI-30XA Calculator

### TI-84 Plus Silver Edition. When dividing negative powers of ten by other negative powers of 10 the calculator it just adds the the negative powers together. How do i fix this? An example: 5*10^-10 /...

To enter an exponent, positive or negative, use the EE (Enter Exponent) key (the shifted function of the , key just above the 7 key). Do 5 2ND [EE] (-) 1 0 / 5 2ND [EE] (-) 1 0 ENTER and you'll see 1.

What I think you're doing (I can't be sure without seeing your keystrokes) is calculating
5*10^-10/5*10^-10 which is interpreted as (5*10^-10/5)*10^-10, which indeed is 10^-20.

Oct 16, 2010 | Texas Instruments TI-84 Plus Silver...

### How do you input -log ?

Use the log function (common logarithm). See screen capture for markings on key.

To evaluate the negative of a logarithm
Enter the number (argument) of the logarithm
Press the = key to have it calculated.
While result is still displayed, press the sign change key or (+/-).

Beware that -log(number) is not necessarily a negative value.

Another way to calculate -log is to use the relation
log(1/a)=-log(a) .

Jun 01, 2010 | Casio FX-260 Calculator

### Negative log

Use the log function (common logarithm). See screen capture for markings on key.

To evaluate the negative of a logarithm
Enter the number (argument) of the logarithm
Press the = key to have it calculated.
While result is still displayed, press the sign change key or (+/-).

Beware that -log(number) is not necessarily a negative value.

Another way to calculate -log is to use the relation
log(1/a)=-log(a) .

3 [EXP] [(] [+/-] 2 [) ] [LOG][=] [+/-]

[EXP] is the key to enter exponent of a power of 10 :It is a shortcut, so no 10 is entered. Respect the key sequence above.
[ (] left parenthesis to prevent ambiguity due to the negaticve exponent. Just a security.
[)] is the enclosing right parenthesis
[+/-] is the Sign Change key

May 06, 2010 | Casio FX-260 Calculator

### How do i make the log button negative?

Enter the number, then press the LOG button. Once result is displyed press the change sign key. If result is positive, it will become negative. If result is negative it will become positive. The Change sign key is the one with + -, located between the . and the = on the bottom row of keys.

Apr 01, 2010 | Texas Instruments TI-30XA Calculator

### Please explain which buttons to push on TI-36x solar calculator to find the pKa of benzoic acid. the Ka for benzoic acid is 6.5 X 10 to the -5th ? (Sorry I don't know how to type the exponents for you)

You need the [EE] key to enter powers of 10 exponents.
You need the change sign key [+/-] key.
You need the [LOG] key.

pKa: 6.5 [EE] [+/-] 5 [LOG] [+/-]
There are two change sign: The first (either before or after the exponent 5), the last is entered after you press the log key , so as to negate (make negative if result is positive, and make positive is result is negative) the value.
The result should be 4.1870866 or 4.19

Mar 08, 2010 | Texas Instruments TI-36 X Solar Calculator

### How do i enter pH on a TI 30 calculator

Hello,
1. How to obtain the concentration knowing the pH?
2. How to obtain the pH knowing the concentration
If you are not interested in the theory, jump to the examples at the end of the post.

As you well know the pH is the negative of the log in base 10 of the H+/H3O+ ion concentration. If we use [H+] to represent that concentration, then pH=-log[H+].
To obtain the [H+] you need to calculate the antilog. You write the definition in the form log[H+] =-pH and then calculate 10 to the power of each member. The equality remains valid as both members are treated similarly. Thus
10^( log[H+] ) = 10^(-pH)
Since raising 10 to a power is the inverse function of taking the log in base 10, 10^(log(x))=log(10^(x)) = x (they are inverse of one another), you are left with

[H+]=10^(-pH)

Your calculator has a function [10 to x] accessed by pressing the [2nd] function key. To use it you must enter the negative value of the pH, press the [2nd] function key then the [10 to x], then the = key to get the result (concentration)
Examples

1. Let the pH=5.5, what is the H+ concentration?

With [(-)] being the change sign key, then
[H+]:[ (-) ] 5.5 [2nd][10 to x] [=]
The result is 0.000003162 or 3.16 x 10^(-6)

Calculating the pH

Shortcut:
For all H+/H3O+ concentrations of the form 1.*10^(a) where a is an integer number between 0 and -14, the pH is the negative value of the exponent.
Concentration =10^(-3), pH=3
Concentration=10^(-11), pH=11

For other concentrations such as 3.567*10^(-8), one cannot use the shortcut above, but have to calculate the log of the concentration

[H+/H3O+] = 3.567*10^(-8)
pH= - log(3.567*10^(-8))
This is keyed in as follows (to minimize the number of parentheses)

8 (-) [2nd][10 to x] [*] 3.567 [LOG] [=] (-)
Here you have two (-) change sign, the first is entered after the exponent of 10, the other at the end of the calculation to take the negative of the displayed result. You may notice that it is entered in the reverse order of the defining relation - log(3.567*10^(-8)).
To verify your calculation, the result is 7.447696891 or just 7.45
If you have a problem with the first (-) try entering it before you type in 8.

Hope it helps and thank you for using FixYa

Dec 07, 2009 | Texas Instruments TI-30XA Calculator

### How do I proform the -log of a number ie -log(1.2 X 10-5) to find the pH

Hello,
The pH is defined as the negative log in base 10 of the H+ (H3O+) ion concentration. The concentration of your solution is 1.2x10^(-5). You calculate the log of 1.2x10^(-5) which is -4.9208188754, let us just say it is equal to -4.921.
Once result is displayed press the change sign key (-) or on some calculators [+/-] and calculator will take the negative of the result.

Another less efficient way to do it is to enter
0-log(1.2x10^-5) [ENTER]. The result will be positive.

The change sign (-) is smaller than the regular MINUS sign. It is used with negative exponents and to change the sign (hence its name) of a displayed result.

Oct 06, 2009 | Texas Instruments TI-30XA Calculator

### Trying to enter Chemistry equations and it won't work...

the way i enter my equations is a bit different from what you're doing, i use the fraction button to do division problems, i just feel it makes it easier to read.
anyway, the fraction button is on the far left, 3rd button down (it looks like a white box on top of a line, and below the line is another empty box). press that, and you can type 1.0x10^-14 on the numerator.
it seems that you haven't discovered the EXPONENT button. that button is on the same row as the fraction button, it looks like an x with a white box next to it. press that once you've typed out "1.0x10", and then type -14. the negative button btw is below the fraction button, and looks like this: (-)
press the right arrow twice on the circle thingy at the top of all the keys, and that'll advance you to the denominator. type 2.0x10^-5, using that nifty exponent key. press the equal sign and it'll solve it for you, all in scientific notation (the answer is 5x10^-10). the problem with this calculator is, it won't expand that answer for you with all the decimals and everything, but if its chemistry that shouldn't be a problem.
also, you can certainly use the "x10^x" button on the very bottom of the keypad (its next to the decimal button). by using this key, you won't have to press the exponent button since you can just type in the exponent directly next to the 10.

as for that negative log of 5.6, just input the negative, the log button is right next to the exponent button, and your number and yeah....it's that easy :]

i hope you like this caculator, it has so many functions (have you seen the size of the manual??)
good luck on your chemistry test!

Jun 06, 2009 | Casio FX-115ES Scientific Calculator

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