CHM 111 Homework 1
You must write down all of your mathematical steps to get full credit. Please use separate pieces of paper for your answers and please staple them together.
Due: Fri 9/20
Question 1
Calculate the density of the following substances. Express your answers in g/cm³ and round up your answers to the nearest significant figures:
(a) A 3.00 kg block of chromium displaces 0.4210 L of water. What is the density of chromium?
(b) 4.00 x 10⁻² mL of bromine (a liquid element) weigh 0.1249 g. What is the density of bromine?
Question 2
Round up your answers to the nearest significant figures. Please use the factor-label method/dimensional analysis format for your calculations.
(a) The density of titanium is 4.54 g/cm³. What is the volume of 1.121 g of titanium?
(b) The density of germanium is 5.323 g/cm³. How much does a 3.00 x 10³ cm³ block of germanium weigh (in kg)?
(c) The density of hexane is 0.6548 g/cm³. How many grams are there is 0.250L of hexane?
(d) The density of pentane is 0.626 g/cm³. How many mL are there in 0.450 kg of pentane?
(e) The energy content of natural gas is about 39 MJ/m³ (where 1 MJ = 10⁶J). Suppose you need to produce 5.0 x 10⁵J of energy. How much volume (in m³) of natural gas do you need?
(f) Sea water has a typical salinity of 39 g/L in dissolved salts. Suppose you have 125.0 mL of sea water. How many grams of dissolved salts can you recover?
(g) The atmospheric pressure at the surface of planet Mars is 7.5 mbar (as reported by the Phoenix Mars Mission, http://phoenix.lpl.arizona.edu/). What is the pressure in mmHg (1 bar = 1000 mbar; 750.062 mmHg = 1 bar)?
(h) Suppose you have a 75 J/s light bulb (J/s is also call watt, thus it is a 75 watt bulb). Suppose the light bulb was on for 7.200 x 10³ s (i.e. 2 hours). How much energy (in kJ) has it used?