Looking for a guy friend

Significant figures are digits read directly from the measuring instrument plus one more digit, which is __ by the observer.

Which statement about hf is true? it is zero for any compound in its standard state. it is positive when the bonds of the product store more energy than those of the reactants. it is negative when a compound forms from elements in their standard states. it is zero for any element that is in the liquid state.

Glucose (c6h12o6) is an important biological molecule. (round the answer to nearest hundredth.) what is the percent by mass of carbon in glucose?