An electromagnet is the most powerful type of magnet there is It is a magnet with a current running through it that can be turned on and off Why might it be useful to be able to turn the electromagnet on and off?
O to reduce wearing out of the magnet over time
O to control the strength of the magnet
O to not waste electricity
O to latch onto and let go of objects

the volume of fluid displaced would equal the volume of the gas. use a gas syringe - this is a laboratory instrument that can be used to withdraw a certain volume of gas from a closed system or to measure the volume of gas from a chemical reaction.

the atomic mass is the bottom number on the element.

-steel jelly

tracks, burrows, eggshells, nests, tooth marks, or gastroliths

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol