Question

1. define chromatography and distillation. give an example of where each method may be used.
2. what is the difference between mass and weight? which do you get directly from a balance? what are the units on the measurement?
3. what is an isotope?
4. a new element x is found and in the sample 70% has a mass number of 43, 25% is x - 44, & 5% is x - 47. what is the (average) atomic mass of this new element?
5. what is the law of conservation of mass (matter)? 10 grams of substance a reacts completely with 5 grams of substance b. if the reaction is a + b → c + d. if 12 grams of c is made, how many grams of d would also be made?
6. if you wanted to measure 50.0ml of water for an experiment, which of the following would be the best piece of equipment to use? (and explain why.) a beaker, a balance, a graduated cylinder, or an erlenmeyer flask.
7. no - no - nancy needs to weigh out 5g of a chemical in the lab. she comes into the lab wearing flip - flops, shorts, loose long hair, & her contact lenses. she uses her bare hands to put the chemical directly on the balance to get the 5g. correct everything wrong that she did.
8. calculate the following conversions using proper significant figures.

a. 5dm is how many km?
b. 2l is how many cl?
c. 2.4*10^(-5)g is how many mg?
d. a 5*10^3ml fish tank is how many hl
e. an e coli is 9.5*10^(-11)mg. how many pounds is that? (1kg = 2.204lb)

1. calculate the following density problems using proper significant figures.

a. what is the density of ether (which used to be used as an anesthetic) given that 300.0ml has a mass of 217.5g?
b. mercury has a density of 13.69g/ml. what is the volume of 1.2kg of it?

1. which of the following is the correct full electron configuration for nickel (ni)? ____

then explain what is wrong with the other choices that are not the correct answer.
a. 1s^1,1p^1,2s^2,2p^6,3s^2,3p^6,3d^8,4s^2
b. 1s^2,2s^2,2p^6,3s^2,3p^6,4s^2,4d^10
c. 1s^1,1p^1,2s^2,2p^6,3s^2,3p^6,4s^2,4d^8
d. 1s^2,2s^2,3s^2,4s^2,3d^8
e. 1s^2,2s^2,2p^6,3s^2,3p^6,4s^2,3d^8

Explanation:

27.

Define mass and weight concepts.

28.

State the definition of isotopes.

29.

Use the formula for average atomic mass calculation.

30.

Apply the law of conservation of mass.

31.

Explain the suitability of equipment for volume measurement.

32.

List lab - safety violations.

33.

Use unit - conversion factors.

34.

Apply density formula \(
ho=\frac{m}{V}\) and its rearrangement for volume calculation.

35.

Use the rules of electron - configuration filling and identify incorrect configurations.

Answer:

27.

Mass is the amount of matter in an object, a scalar quantity. Weight is the force exerted on an object due to gravity, a vector quantity. You get mass directly from a balance. The unit of mass is kilogram (kg), and the unit of weight is newton (N).

28.

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.

29.

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30.

The law of conservation of mass states that in a chemical reaction, the total mass of the reactants is equal to the total mass of the products.
Let the mass of D be \(x\) grams.
The mass of reactants \(=10 + 5=15\) grams.
The mass of C is 12 grams.
By the law of conservation of mass, \(15=12 + x\), so \(x = 3\) grams.

31.

A graduated cylinder should be used. A beaker has large - measurement errors for precise volume measurements. A balance is used to measure mass, not volume. An Erlenmeyer flask is not designed for precise volume - measurement of liquids. A graduated cylinder is calibrated for measuring the volume of liquids accurately.

32.

Nancy made the following mistakes:

1. She should not wear flip - flops in the lab as they do not provide proper foot protection.
2. She should tie her long hair back to prevent it from getting into chemicals or equipment.
3. She should not wear contact lenses in the lab as chemicals can splash into her eyes and damage the lenses or her eyes.
4. She should use appropriate weighing paper or a container to hold the chemical instead of putting it directly on the balance with her bare hands.

33.

a. \(1\ dm = 10^{-4}\ km\), so \(5\ dm=5\times10^{-4}\ km\)
b. \(1\ L = 100\ cL\), so \(2\ L = 200\ cL\)
c. \(1\ g=1000\ mg\), so \(2.4\times 10^{-5}\ g=2.4\times10^{-5}\times1000 = 0.024\ mg\)
d. \(1\ mL = 10^{-4}\ hL\), so \(5\times10^{3}\ mL=5\times10^{3}\times10^{-4}=0.5\ hL\)
e. First convert mg to kg: \(9.5\times10^{-11}\ mg=9.5\times10^{-11}\times10^{-3}\ kg = 9.5\times10^{-14}\ kg\)
Then convert kg to pounds: \(9.5\times10^{-14}\ kg\times2.204\ lb/kg\approx2.09\times10^{-13}\ lb\)

34.

a. The density formula is \(
ho=\frac{m}{V}\). Given \(m = 217.5\ g\) and \(V = 300.0\ mL\), \(
ho=\frac{217.5\ g}{300.0\ mL}=0.725\ g/mL\)
b. First convert mass to grams: \(1.2\ kg = 1200\ g\)
Since \(
ho=\frac{m}{V}\), then \(V=\frac{m}{
ho}\). Given \(
ho = 13.69\ g/mL\), \(V=\frac{1200\ g}{13.69\ g/mL}\approx87.66\ mL\)

35.

The correct electron - configuration for nickel (Ni) is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{8}\) (option e).

• Option a: There is no \(1p\) orbital.
• Option b: The \(3d\) sub - shell should be filled before the \(4d\) sub - shell, and nickel has 28 electrons, and this configuration has more electrons than nickel.
• Option c: There is no \(1p\) orbital, and the order of filling is incorrect.
• Option d: The \(2p\) and \(3p\) sub - shells are missing electrons.