**98 points**

given 1.00 gram of (nh4)2 co3, how many grams of this sample would be due to hydrogen?

OP already did it - CONGRATS!!

here are the steps 2 get the same ans:

(NH4)2 CO3 has 2x N, 8x H, 1x C and 3x O per molecule

so its molecular mass = 2x14 + 8x1 + 1x12 + 3x16

=28+8+12+48

=96g

of that 96g, 8x1=8g is due to Hydrogen

so by ratio n proportion, 1.00g will have 1x8/96 = 1/12g = 0.083g of H

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