Question

1) A student performs an experiment to determine the density of a sugar solution. She obtains the following results 136 g ml, 1.81 gmL 1.80 g/mL, 1.81 g/mL. If the actual value for the density of the sugar solution is 1.80 g/ml, which statement below best describes her results? A) Her results are precise, but not accurate. C) Her results are both precise and accurate B) Her results are neither precise nor accurate. D) Her results are accurate, but not precise. What does "X" represent in the following atomic symbol? 35 17 A) Te tellurium B) Ar argon C) Br bromine D) Cl chlorine 3) A covalent bond is best described as A) a bund between a metal and a nonmetal. B) the sharing of electrons between atoms. C) a bond between a metal and a polyatomic ion D) the transfer of electrons. E) a bond between two polyatomic ions.

Answer 1

1) The term acccuracy is defined as the closeness of an acquired experimental with that of a standard or actual value. In this case the known value is given as 1.80 g/ml.

Also the mean of the given readings is (1.79 + 1.81 + 1.80 + 1.81)/4 g/ml = 1.8025 g/ml. This value is very close to the actual value of 1.80 g/ml. Hence these results are accurate.

The term precision on the other hand is defined as the closeness of the experimentally obtained values with each other. In this case the experimentally acquired values are 1.79, 1.81, 1.80 and 1.81 g/ml. In this case we see that all the values are very close to each other and no experimental value is obtained which is very far off from these. Difference between highest and lowest reading is 1.79 - 1.81 = 0.02. This is very less. Thus, these readings are precise.

Thus, Her results are both precise and accurate. (Ans C)

2) The symbol given is represented as ³⁵ X _17. The number on top (35) is the the mass number (A) of the element and the one at the bottom is the atomic number (Z). i.e ^A X _z.

From the periodic table. The element with atomic number 17 is Chlorine. (Ans D).

3) By defination: A covalent bond is a bond which is formed by sharing of electrons between two atoms. Hence, (Ans = B)