2023 HESI A2 CHEMISTRY EXAM PREP Q&A

2023 HESI A2 CHEMISTRY EXAM PREP Q&A 1. 1. QUESTION Normal body temperature is considered to be 98.6oF. What is the normal body temperature in degrees Celsius? o 100° C o 37° C o 32° F o 21° C Answer: 37° C To convert between Fahrenheit and Celsius scales, use the formula, [°C] = ([°F] – 32) × 5/9. Inserting 98.6oF for the [oF] term, you get 37oC as the answer. [°C] = (98.6°F – 32) × 5/9 [°C] = (66.6) × 5/9 [°C] = 37 2. 2. QUESTION The mass of a grain of sand is 1.672 × 10-4 kg. Express this number in standard notation. o 1,672 kg o 1,672,000 kg o 0. kg o 0. kg Answer: 0. kg Scientific notation is a way to write very large or very small numbers. This method of notation is useful to scientists when they are writing very large or very small numbers, so they don’t have to write so many zeroes! To convert from scientific notation to standard notation, look at the exponent: o The value of the exponent tells you how many spaces to move the decimal. Since the value of the exponent in 1.672 × 10-4 is 4, this tells us we will need to move the decimal 4 spaces. o The sign of the exponent tells you which direction we are going. A positive exponent tells us to move the decimal to the right. A negative decimal tells us to move the decimal to the left. Since the sign of the exponent in 1.672 × 10-4 is negative, this means we will be moving the decimal to the left. So, since the exponent is negative and has a value of 4, so we just need to move the decimal 4 places to the left to arrive at the answer, 0.. You may use the examples below as a visual reference for how scientific notation represents numbers. 3. 3. QUESTION Which of the following is the SI unit used to measure the amount of a substance? o Meter o Mole o Gram o Kilogram Answer: Mole The International System of Units (SI, abbreviated from the French Système international) is the modern form of the metric system and is the most widely used system of measurement in the world. It comprises a system of units of measurement built on seven base