predict how the following pairs of atoms will combine by writing the fromulas for resulting compunds
can you help me with the first to to use as an example for the 30 problems please
H (+1) and SO 4 ( - 2)
the 4 is below the O
Al ( +3) and SO4 ( -2 )
the 4 is below the O
Compounds must be zero charge; therefore, you make the charges add to zero.
If H is +1 and SO4 is -2, then H2SO4 is what it takes. You can check it out. The subscript of 2 on H multiplies the number by 2; therefore, 2 x +1 charge = 2 + charges for H. For SO4, it is -2. Then +2 and -2 = zero.
For Al and SO4 (I'll not write the subscripts that way anymore), it's a little more complicated but not much. The problem, as you may have noticed, is that in the case of H2SO4, it was easy to multiply +1 for H to get the 2 we were looking for for SO4 (since it was -2). With Al and SO4, it takes 3/2 x 2 to get 3 and we are looking for WHOLE numbers and not fractions. The way to overcome this is to think of numbers that we can multiply both numbers by to get a common number. That common number is 6; therefore, we multiply 3 x 2 = 6 and 2 x 3 = 6.
Al2(SO4)3 is aluminum sulfate.
Note that 2Al x 3+ = 6+ charges. SO4(at -2 each) x 3 = 6- charges; then 6+ and 6- = zero. Here is an easy way to do that.
Place the +3 above Al and the -2 above SO4. Draw a large X through the compound. You can do this mentally. The left leg of the X runs from the +3 above Al to where the subscript goes for sulfate. The right leg of the X runs from the -2 of sulfate to the subscript of Al (which i 1 before you have done anything to it). Now just carry the numbers. For the left leg the +3 at the top of the left leg goes to sulfate at the bottom of the leg. (You must place a set of parentheses around SO4 because you want to multiply all of sulfate (the S and the O4) by 3.) Then the -2 from sulfate at the top of the right leg of the X goes to the bottom of Al for that subcript. That gives you Al2(SO4)3. I hope this helps. Post again if you still have questions.