Wednesday

September 17, 2014

September 17, 2014

Posted by **ann** on Friday, December 16, 2011 at 11:28am.

write a direct variation equation that

relates atoms of O oxygen to atoms of hydogen H Mary combined 8 atoms of hydrogen and 4 atoms of oxygen to get 4 molecules of water

is this equation correct?

O + 2H = WM

- algebra -
**Willie**, Saturday, December 17, 2011 at 10:36amIn chemistry class you might write an equation in that fashion to suggest that 1 molecule of water is composed of the "sum" of 1 oxygen atoms and 2 hydrogen atoms.

In your math work, since you are doing the topic of "direct variation" you are expected to think about how the quantities vary. That means an equation of the form y = kx, where k is a constant and x and y are the variables.

In this case, what is asked for is the ratio of hydrogen to oxygen, which is constant no matter how many molecules you are talking about.

For example, you could have (oxygen, hydrogen) values of (1, 2), (2, 4), (3, 6), (4, 8), etc.

This can be expressed as H = 2O, in other words, number of hydrogen atoms is two times whatever the number of oxygen atoms.

y = k * x

H = 2 * O

In this case, the equation is expressing how hydrogen "varies directly" with oxygen. The constant of variation is 2.

You could also write this:

y = k * x

O = (1/2) * H

That would express how oxygen varies directly with hydrogen. The constant of variation is 1/2.

Graph of y = kx is a line through (0, 0) always. The slope of the line is k.

So instead of an "addition" equation, direct variation is always a "multiplication" equation.

Note: If you have a situation that does not pass through (0, 0), it is not considered "direct variation."

So, y = 3x + 5 is not direct variation.

- algebra -
**ann**, Sunday, December 18, 2011 at 6:21amThank you very much for explaining it to me. I am taking my first algebra course and I am having a difficult time in undestanding my text. You made this so clear. I really appreciate it. thanks Ann

- algebra -
**sarah**, Saturday, July 21, 2012 at 5:41pmCOrrect ! great job

**Answer this Question**

**Related Questions**

Algebra - Joyce combines 9 atoms of hydrogen and 3 atoms of nitrogen to make 3 ...

Science - How many atoms of aluminum can be produced by the decomposition of 47....

Math - Glucose is a common type of sugar. One glucose molecule is made up of 24 ...

Science URGENT - Write down the number of hydrogen and oxygen atoms of the ...

Intro. Chemistry - Based on the law of definite composition, Dalton proposed ...

chem - one atom of silicon can properly be combined in a compound with A. one ...

math - What is one mole of H2O composed of? A. 2 hydrogen atoms and 1 oxygen ...

chemistry - what is the mass in grams? a) 3.011 x 10^23 atoms F b)1.50 x 10^23 ...

chemistry - calculate number of atoms in 4.67 mol of Ca(NO3)2 I got: 2.81 X 10^...

chemistry - what is the mass in grams? a) 3.011 x 10^23 atoms F b)1.50 x 10^23 ...