how many moles of water are produced when 05 moles of methane ch4 react with excess oxygen

ATI TEAS 7

TEAS 7 science practice questions

1. How many moles of water are produced when 0.5 moles of methane (CH4) react with excess oxygen?

A. 0.5 moles
B. 1 mole
C. 2 moles
D. 3 moles

Correct answer: B

Rationale: The balanced chemical equation for the combustion of methane is: CH4 + 2O2 -> CO2 + 2H2O. This equation shows that 1 mole of methane produces 2 moles of water. Therefore, when 0.5 moles of methane react, they will produce 1 mole of water. The ratio of water to methane is 2:1, meaning that for every mole of methane that reacts, it produces 2 moles of water. Since only 0.5 moles of methane are reacting, the amount of water produced will be half of what would be produced if 1 mole of methane reacted, resulting in 1 mole of water being produced. Choice A is incorrect because it does not consider the stoichiometry of the reaction. Choices C and D are incorrect as they do not align with the balanced chemical equation and the stoichiometric ratios involved in the reaction.

2. What does the following sentence most nearly mean? 'The preparatory instars of such insects are aquatic; the adult instar is aerial.'

A. The volume of water is necessary for preparing the insect for transition rather than the volume of the air.
B. The insect's body is shaped like a star in both water and air.
C. The stage of preparation between molting occurs in water, while the final stage happens in the air.
D. These insects first breathe in water through gills and then continue to use the same organs to breathe in the air.

Correct answer: C

Rationale: The sentence indicates that the insects undergo different stages of development, with the preparatory instars being aquatic and the adult instar being aerial. This highlights the adaptability of these insects to different environments. Choice A is incorrect as it focuses on the volume of water and air rather than the stages of development in different environments. Choice B is unrelated to the content of the sentence and does not capture the meaning accurately. Choice D is incorrect as it specifically mentions breathing through gills, which is not explicitly stated in the sentence. Therefore, choice C is the best interpretation of the sentence.

3. What is the equivalent of 3,450 milliliters in liters (L)?

A. 0.345 liters
B. 3.45 liters
C. 34.5 liters
D. 345 liters

Correct answer: B

Rationale: To convert milliliters to liters, you need to divide by 1,000 since there are 1,000 milliliters in a liter. Therefore, 3,450 mL ÷ 1,000 = 3.45 liters. Choice A (0.345 liters) is incorrect as it incorrectly moves the decimal point. Choice C (34.5 liters) is incorrect as it overestimates the conversion. Choice D (345 liters) is incorrect as it overestimates by an order of magnitude.

4. Solve the equation 3(2x+5)=11x+5 for x. Which of the following is correct?

A. 1
B. 2
C. -1
D. -2

Correct answer: B

Rationale: To solve the equation, distribute 3 to both terms inside the parentheses: 6x + 15 = 11x + 5. Then, move 11x to the left side by subtracting it from both sides: 6x - 11x = 5 - 15. Simplify to get -5x = -10. Divide by -5 to isolate x: x = 2. Therefore, the correct answer is x = 2. Choices A, C, and D are incorrect because they do not match the correct solution obtained by solving the equation step by step.

5. When magnesium metal reacts with hydrochloric acid, hydrogen gas is produced. What evidence suggests a chemical reaction is occurring?

A. A change in color
B. The formation of a gas
C. Dissolving in a liquid
D. No change in temperature

Correct answer: B

Rationale: The formation of a gas is evidence of a chemical reaction occurring. In this case, when magnesium metal reacts with hydrochloric acid, hydrogen gas is produced, indicating a chemical change is taking place. The production of gas is a clear indication of a chemical reaction, as new substances are being formed. A change in color might suggest a physical change, dissolving in a liquid could be a physical or chemical change depending on the context, and no change in temperature does not necessarily indicate a chemical reaction, as some reactions are endothermic or release small amounts of heat that may not be easily noticeable.