Aclassmate finds that it takes 1.090 seconds for a tossed ball to touch the ground. how many significant figures are in this measurement?

Answer : The measurement has 4 number of significant figures.

Explanation :

Significant figures : The figures in a number which express the value -the magnitude of a quantity to a specific degree of accuracy is known as significant digits.

Rules for significant figures:

As we are given the measurement 1.090 seconds.

According to rule, all zero’s between integers and zero’s after the decimal point are always significant.

So, the measurement has 4 number of significant figures.

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