chem 105 HW2&3 Mastering

Perform the calculation to the correct number of significant figures. (12.01×0.3)+4.811

(12.01×0.3)=3.6 3+4.811= 8 8( one sig fig)

What is the atomic mass of the element that consists of the following isotopes in the indicated natural abundances? Isotope Isotopic mass (amu) Relative abundance (%) 1 57.93..... 67.76 2 59.93 .....26.16 3 60.93......1.25 4 61.93 .......3.66 5 63.93 ......1.16

(57.93*0.6776)+(59.93*0.2616)+(60.93*0.0125)+(61.93*0.0366)+(63.93*0.0116) = 58.7amu

metals

-good conductors of heat and electricitythey -can be pounded into flat sheets -they can be drawn into wires -they tend to lose electrons when they undergo chemical changes -are found on the left side and the middle of the periodic table

nonmetals

-poor conductivity of heat and electricity -they all tend to gain electrons when they undergo chemical changes -are found on the upper-right side of the periodic table -some of them are solids at room temperature, while others are liquids or gases

metalloids

-some of them are classified as semiconductors -lie along the zigzag diagonal line of the periodic table -they show mixed properties

Perform the calculation to the correct number of significant figures. 3.10007×9.441×0.0301÷2.31

0.381

Perform the calculation to the correct number of significant figures. 2.5110×21.20÷(44.11+1.223)

1.174

1.69×10−2+3×10−4−2.9×10−3

1.43×10−2

Give the nuclear symbol for the isotope of beryllium for which A=10?

10/4Be

Perform the calculation to the correct number of significant figures. 0.881 +132.1 −12.02−−−−−−−

121.0

A vineyard has 145 acres of Chardonnay grapes. A particular soil supplement requires 5.50 g for every square meter of vineyard. How many kilograms of the soil supplement are required for the entire vineyard? (Recall that 1 km2 = 247 acres.)

145 acres×1 km2247 acres×(1000 m)2(1 km)2×5.5 g1 m2×1 kg1000 g = 3230 or 3.23 * 103 kg

The conversion factor relating feet to meters is 1ft=0.305m. Keep in mind that when using conversion factors, you want to make sure that like units cancel leaving you with the units you need. You have been told that a certain house is 164 m2 in area. How much is this in square feet?

1760ft^2 164/.305/.305=1762.966 3sig fig

How many cubic centimeters are there in 2.11 yards3?

2.11 yards3×(3 ft)3(1 yard)3×(12 in)3(1 ft)3×(2.54 cm)3(1 in)3 = 1613210.75 1.61 EE6 cm^3

1.71×10−3/7.9×102

2.2×10−6

A sprinter set a high school record in track and field, running 200.0 m in 21.8 s . What is the average speed of the sprinter in kilometers per hour?

200m/1000= 0.2km 21.8s/3600= .0060h 0.2/0.0060= 33.33 km/h

While in Europe, if you drive 121 km per day, how much money would you spend on gas in one week if gas costs 1.10 euros per liter and your car's gas mileage is 28.0 mi/gal ? Assume that 1euro=1.26dollars.

28.0mi/gal(1km/0.6214mi)(1liter/3.78gal)=11.92km/L (121km/11.92km/L)(7days/week)(1.10 euros/liter)(1.26dollars/euros)= 98.48dollars a week

A specific brand of gourmet chocolate candy contains 7.00 g of dietary fat in each 22.7-g piece. How many kilograms of dietary fat are in a box containing 4.00 lb of candy?

4.00lb*0.454kg = 1.816kg 22.7/1000=0.0227 kg 1.816 kg/0.0227 kg =80kg 7.00g/1000=0.007kg 80kg x 0.007 kg = 0.56 kg

What is the volume in L of 4.1 kg of ethylene glycol?

4.1kg/.001kg=4100g 4100g/1.11g/cm^3 = 3693.7cm^3 3693.7cm^3*0.001L/cm^3 = 3.69L 3.7L two sig fig

In Europe, gasoline efficiency is measured in km/L. If your car's gas mileage is 40.0 mi/gal , how many liters of gasoline would you need to buy to complete a 142-km trip in Europe? Use the following conversions: 1km=0.6214mi and 1gal=3.78L.

40mi/gal(1km/0.6214mi)(1liter/3.78gal)=17.02km/L 142/17.02 = 8.34 L

What is the mass in g of 426 mL of ethylene glycol? Ethylene glycol (antifreeze) has a density of 1.11 g/cm3.

426*1.11= 472.8 4.73g (3sig fig)

The conversion factor relating miles to meters is 1mile=1610m. The speed of light is 3.00×108 m/s. How fast is this in miles per hour (miles/h)?

6.71×108 miles/h

Part complete [(1.35×105)(0.000364)/0.080](110.3)

6.8×104 two sig fig

A certain element X has four isotopes. 0.5600% of X has a mass of 83.91343 amu. 9.860% of X has a mass of 85.90927 amu. 7.000% of X has a mass of 86.90890 amu. 82.58% of X has a mass of 87.90562 amu. What is the average atomic mass of element X?

87.62........Sr

Convert 90 cm3 to m3.

90cm3/10EE6= 9EE-5

The two isotopes of chlorine are 3517Cl and 3717Cl. Which isotope is the most abundant?

Since the atomic mass of chlorine, 35.45 amu, is closer to 35 than it is to 37, 35Cl must be the most abundant isotope. 35Cl does in fact account for 75.53% of Earth's chlorine. The full calculation is (0.7553)(34.96885)+(0.2447)(36.96590)=35.45amu

What is the density of the steel in g/cm3?

Volume of cylinder from basic geometry: V= (pi)(r^2)(h) =(pi)(0.5588cm)^2(5.4864cm) = 5.3842cm3 Thus, plug in to our first formula: Density = (41.0g) / (5.3842cm3) = 7.6149 g/cm3 7.6 two sig fig

Potassium has three naturally occurring isotopes with masses of 38.96 amu, 40.96 amu, and 39.96 amu and natural abundances of 93.30 %, 6.70 %, and 1.2×10−2 %, respectively. Calculate the atomic mass of potassium.

atomic mass of potassium=(0.9330)38.96 amu+(6.70×10−2)40.96 amu+(1.2×10−4)39.96 amu Significant Figures Feedback: Your answer 39.09amu was either rounded differently or used a different number of significant figures than required for this part.

Noble gases halogens alkali metals alkali earth metals

group8A, mostly unreactive group7A, very reactive group1A, all reactive group 2A, fairly active