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Two students determine the percentage of lead in a sample as a laboratory exercise.  The true percentage is 22.50%.  The students’ results for the three determinations are as follows:   Student A)  22.52%, 22.48%, 22.54% Student B)  22.64%, 22.58%, 22.62%   Which of the following statements represents the best analysis of the data?  

Which of the following elements has been chosen as the isotope standard in measuring atomic mass?  

Write the formula for copper (II) sulfate pentahydrate. A) Cu2SO3∙H5 B) Cu2S∙H2O C) CuS∙5H2O D) (CuSO4)5 E) CuSO4∙5H2O  

A)  Give an example of a scientific theory.  Complete sentences not needed. B)  Are theories considered facts?  State yes or no.

How many anions are there in  3.50 g of MgBr2? A) 1.14 × 1022anions B) 2.29 × 1022anions C) 3.17 × 1025anions D) 6.34 × 1025 anions

Give the name for HNO3. A) nitric acid B) nitrous acid C) hydrogen nitrate D) hydrogen nitrite E) hydrogen nitride

Use Lewis theory to determine the chemical formula for the compound formed between Al and  F. A) Al3F2 B) Al2F3 C) Al F2 D) Al F E) Al F3

Describe a sigma bond. A) side by side overlap of d orbitals B) end to end overlap of p orbitals C) s orbital overlapping with the side of a p orbital D) overlap of two d orbitals E) p orbital overlapping with an f orbital

How many molecules of N2O4 are in 76.3 g N2O4? The molar mass of N2O4 is 92.02 g/mol. A) 5.54 × 1025N2O4 molecules B) 7.26 × 1023N2O4 molecules C) 1.38 × 1024N2O4 molecules D) 4.59 × 1025 N2O4 molecules E) 4.99 × 1023N2O4 molecules  

How many molecules of butane are contained in 25.0 mL of butane? The density of butane is 0.6011 g/mL and the molar mass is 58.12 g/mol. A) 2.59 × 1023molecules butane B) 1.46 × 1027molecules butane C) 6.87 × 1023molecules butane D) 1.56 × 1023molecules butane E) 7.14 × 1025molecules butane