Three samples of 0.12 g, 1.8 g, and 0.562 g are mixed together. the combined mass of all three samples, expressed to the correct number of significant figures, should be recorded as

The mass of three samples are 0.12 g, 1.8 g and 0.562 g. (given)

During addition (mathematical operation) of significant figures following rules are followed:

1. The number of significant figures are counted.

2. Addition is done.

3. Round the answer to the least number of decimal places.

Following the above rules, the addition of mass of the three samples is as follows:

Hence, is the combined mass of all the three samples.

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

i'm pretty sure it is letter c.) car