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Chemistry Study Questions

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1. What scientific principle or law is used in the process of balancing chemical equations?
2. In balancing equations, why should you not change subscripts in chemical formulas?
3. Define the terms limiting reactant and excess reactant.
4. Why are the amounts of products formed in a reaction determined only by the amount of the limiting reactant?
5. Why should you base your choice of what compound is the limiting reactant on its number of initial moles, not on its initial mass in grams?
6. Explain why the general trend exists for elements getting smaller as you move across a period on the periodic table.
7. Explain the importance of the VSEPR Theory.

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Solution Preview

1. Conservation of mass is used in a reaction, if you start with a total of 'x' grams of reactant, the sum of the masses of all products should equal 'x' grams.

2. Changing subscripts of a formula leads to a completely different compound. Even though the number of atoms may remain the same, the compounds will be different. So if 2 moles of CO2 form, you should say 2CO2 rather than C2O4.

3. The limiting reactant is the reactant whose mass (and hence moles) decides the number of moles (and hence mass) of product that can form. It is taken in the least ...

Solution Summary

The expert determines the scientific principles or law used in the process of balancing chemical equations. The terms limiting reactant and excess reactants are determined.

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Chemistry review questions

Question 2
An imaginary element X consists of two isotopes having masses of 110.00 amu and 112.00 amu. ("amu" is an atomic mass unit.) A sample of X was found to consist of 79.94% 110X and the rest is 112X. What would be the average atomic mass of X in this sample?
Give your answer to four significant figures. Do not enter any units in the box below.
Ans:

Question 6
A compound is composed of 52.2% carbon, 34.8% oxygen and 13.0% hydrogen, by mass. What is the empirical formula of the compound?

a. ) CHO

b. ) C2H6O1

c. ) C12H22O11

d. ) C6H11O7

e. ) CH2O3

Question 7
Identify the type of reaction expected, if any, for each of the following pairs of reactants..
Assume there is enough energy input to get the reaction going, if it is favourable at room temperature (i.e. consider thermodynamics, not kinetics). If the reverse reaction is preferred, assume no reaction.

Preview columns:
â?¢ NaHSO4(aq) + CH3NH2(aq)
â?¢ K3PO4(aq) + NiCl2(aq)
â?¢ Pb(NO3)2(aq) + Zn(ClO4)2(aq)
â?¢ P4(s) + O2(g)
â?¢ Mn(s) + NiCl2(aq) â?¢ precipitation
â?¢ acid base
â?¢ no reaction
â?¢ oxidation reduction

Question 13
Select the net ionic equation for the reaction which occurs when aqueous solutions of mercurous acetate and sodium iodide are mixed :

a. Hg2(CH3COO)2 (aq) + 2 NaI (aq) --> 2 HgI (s) + 2 CH3COONa (aq)

b. Hg22+ (aq) + 2 I- (aq) --> Hg2I2 (s)

c. 2 Na+ (aq) + 2 CH3COO- (aq) --> 2 CH3COONa (aq)

d. Na+ (aq) + CH3COO- (aq) --> CH3COONa (aq)

e. Hg+ (aq) + I- (aq) --> HgI (s)

Question 18
Calculate the volume (in mL) of 0.567 M HCl(aq) required to react with 46.6 mL of 0.383 M Na2CO3(aq).
Be careful to enter the correct number of significant figures. Do not enter any volume units!

Answer:

Question 21
From the following species (molecules and/or ions) choose the one that has the largest (most positive) oxidation number for the underlined atom.

a. C2H6

b. H2SO4

c. NO2

d. HIO3

e. XeF4

Question 29
What is the oxidizing agent in the following spontaneous reaction?
OCl-(aq) + I2(s) + 2 OH-(aq) --->Cl-(aq) + 2 OI-(aq) + H2O(l)

a. ) I2

b. ) OCl-

c. ) OI-

d. ) OH-

e. ) Cl-

Question 30
Which two of the statements are FALSE regarding the balanced equation, corresponding to the following unbalanced reaction?
Co2(SO4)3(aq) + Pb(s) --> CoSO4(aq) + PbSO4(s)

a. ) Cobalt decreases its oxidation number from +3 to +2 in this reaction.

b. ) Co3+(aq) is the oxidizing agent in this reaction.

c. ) Co2+(aq) is a stronger reducing agent than Pb(s).

d. ) One mole of Co2(SO4)3(aq) consumes one mole of Pb(s).

e. ) Co3+(aq) is a weaker oxidizing agent than PbSO4(s).

Question 10
When copper is heated with an excess of sulfur, Cu2S is formed. How many grams of Cu2S could be produced if 250. g of copper is heated with 100. g of sulfur?

a. 626. g

b. 125. g

c. 156.5 g

d. 313. g

e. 532. g

Question 11
In the direct reaction of silicon with Cl2 the yield of SiCl4 is 40 percent. How many grams of SiCl4 are obtained in the reaction of 2.8 g of silicon with excess chlorine?

a. 170 g

b. 17 g

c. 34 g

d. 6.8 g

e. 3.4 g

Question 12
Solid glucose, C6H1206(s) is burned in excess oxygen in a closed container. After the reaction, the total gas volume is 10.0 L at a temperature of 298K. What is the partial pressure, in atmospheres, of the CO2(g) produced by the complete combustion of 5.1 grams of glucose?
Be sure to enter the correct number of significant figures, but do not enter the units (atm)

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