(87.5−22.541)÷ 0.0058    Express your answer to the appropriate number of significant figures.

(A)18.7g NO2 express your answer in moles to three significant figures.  (B)1.88 kgCO2  express your answer in moles to three significant figures. (C) 48.8 g KNO3 express your answer in moles to three significant figures. (D) 116.2 kgNa2SO4 express your answer in moles to four significant figures.

You have a stock solution certified by a manufacturer to contain 245.0±0.2 ?g SO2−4/mL. You would like to dilute it by a factor of 100 to obtain 2.450 ?g/mL. Two possible methods of dilution are stated. For each method, calculate the resulting absolute uncertainty in concentration. Use the manufacturer's tolerances in the table for uncertainties.   Glassware Tolerance 1‑mL transfer pipet ±0.006 mL±0.006 mL 10‑mL transfer pipet ±0.02 mL±0.02 mL 100‑mL volumetric flask ±0.08 mL±0.08 mL Method A: Dilute 10.00 mL up to 100mL with a transfer pipet and volumetric flask. Then take 10.00 mL of the dilute solution and dilute it again to 100 mL.   absolute uncertainty: ±.-----?g/mL   Method B: Dilute 1.000 mL up to 100 mL with a transfer pipet and volumetric flask.   absolute uncertainty: ±------?g/mL

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Use the meaning of the prefix "nano-"  to select the value of "x" in this equation:                   1 m   =   1 x 10x  nm   .   The value of  " x  "  is      (a)  +9                 (b)  -6              (c)  +6               (d)  -9

You determine the acetic acid (HOAc) content of vinegar by titrating with a sodium hydroxide standard solution to a phenolphthalein (an indicator) end point. An approximately 5-mL sample of vinegar is weighed on an analytical balance in a weighing boat and this is found to be 5.0268 g. The standard deviation in making a single weighing is 0.2 mg. The sodium hydroxide must be accurately standardised (this means its concentration must be accurately determined) by titrating known mass of high-purity potassium hydrogen phthalate, and three such titrations give molar concentrations of 0.1167, 0.1163 and 0.1164 mol L-1. A volume of 36.78 mL of sodium hydroxide is used to titrate each sample. The standard deviation of the burette used is 0.02 mL. Calculate the percentage of acetic acid in the vinegar and its standard deviation.

A solution is prepared by mixing 20.0 mL of 0.1 00M Fe(NO3)3 with 20.0 mL of 0.00300M KSCN and 10.0 mL of DI water. Calculate the initial concentration of SCN^- in this solution? Give answer with correct amount of significant figures. 

Two students were tasked to weigh 100 mg of sodium chloride (NaCI). Student A pressed the tare button after weighing the weighing paper and obtained the following data. What is the mass (g) of NaCl from Student A? Mass of weighing paper (g) 0.0011 Mass of weighing paper + NaCl (g) 0.1050 Mass of the NaCI (g) Your answer While Student B did not press the tare button after weighing the weighing paper and obtained the following data. What is the mass (g) of NaCl from Student B? * Mass of weighing paper (g) 0.0011 Mass of weighing paper + NaCI (g) 0.1010 Mass of the NaCI (g) Your answer

Q1. The net potential energy between two adjacent ions, EN, is represented by A В EN pn where En is the net energy in Joule (J), A and B are constants with values of 1.436 J.m and 7.32 × 106 J.nm°, r is the interatomic distance between the two ions in nanometer (nm), and n is a positive number with a value of 8. Using these information, determine the equilibrium spacing between the two ions in nanometer (nm).

Q1. The net potential energy between two adjacent ions, EN, is represented by A В E N pn where EN is the net energy in Joule (J), A and B are constants with values of 1.436 J.nm and 7.32 × 106 J.nm, r is the interatomic distance between the two ions in nanometer (nm), and n is a positive number with a value of 8.