Q: Which of the following correctly expresses 0.000250 g in scientific notation with the correct number of significant figures?

$$2.50 \times 10$$^{-4}$$\ \mathrm{g}$$

Question 1

A student measures the mass of a sample as 0.2050 g. How many significant figures are in this measurement?

Accepted Answer

4

Question 2

Which of the following correctly expresses 0.000250 g in scientific notation with the correct number of significant figures?

Accepted Answer

$$2.50 	imes 10$$^{-4}$$\ \mathrm{g}$$

Question 3

A cube of aluminum has sides of length $$2.00\ \mathrm{cm}. If $$the density of aluminum is $$2.70\ \mathrm{g/cm}^3$$, what is the mass of the cube?

Accepted Answer

$$10.8\ \mathrm{g}$$

Question 4

Which of the following is a homogeneous mixture?

Accepted Answer

Salt dissolved in water

Question 5

Which of the following statements about the Law of Conservation of Mass is correct?

Accepted Answer

The mass of the products in a chemical reaction is always equal to the mass of the reactants.

Question 6

A sample of gas occupies $$5.60\ \mathrm{L} at $$STP. How many moles of gas are present?

Accepted Answer

$$0.250\ \mathrm{mol}$$

Question 7

Which of the following is the correct electron configuration for a neutral atom of phosphorus ($$Z=15$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^3$$

Question 8

Which of the following compounds is a ternary oxyacid?

Accepted Answer

$$\mathrm{H_2SO_4}$$

Question 9

A student needs to convert $$250\ \mathrm{mL} to $$liters. What is the correct conversion?

Accepted Answer

$$0.250\ \mathrm{L}$$

Question 10

Which of the following best describes an exothermic reaction?

Accepted Answer

A reaction in which the products have less potential energy than the reactants, and heat is released.

Question 11

Which of the following is the empirical formula for a compound that is $$40.0\%$$ carbon, $$6.7\%$$ hydrogen, and $$53.3\%$$ oxygen by mass?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 12

A $$10.0\ \mathrm{g}$$ sample of a compound contains $$2.00\ \mathrm{g} of $$hydrogen. What is the percent by mass of hydrogen in the compound?

Accepted Answer

$$20.0\%$$

Question 13

Which of the following is a correct balanced chemical equation for the reaction of sodium with chlorine gas to form sodium chloride?

Accepted Answer

$$2\mathrm{Na}(s) + \mathrm{Cl}_2(g) \rightarrow 2\mathrm{NaCl}(s)$$

Question 14

Which of the following ions is a polyatomic anion?

Accepted Answer

$$\mathrm{CO_3$^{2-}}$$

Question 15

A $$1.50\ \mathrm{mol}$$ sample of helium contains how many atoms?

Accepted Answer

$$9.03 	imes 10$$^{23}$$

Question 16

Which of the following is a double replacement reaction?

Accepted Answer

$$\mathrm{$$AgNO_3$$}(aq) + \mathrm{Na_2CO_3}(aq) \rightarrow \mathrm{Ag_2CO_3}(s) + 2\mathrm{$$NaNO_3$$}(aq)$$

Question 17

A $$2.00\ \mathrm{oz}$$ sample is converted to grams using the following relationships: $$1\ \mathrm{lb} = 16\ \mathrm{oz}$$ and $$1\ \mathrm{lb} = 454\ \mathrm{g}. $$What is the mass in grams?

Accepted Answer

$$56.8\ \mathrm{g}$$

Question 18

Which of the following best describes a physical change?

Accepted Answer

Ice melting to form liquid water

Question 19

A $$25.0\ \mathrm{mL}$$ sample of carbon tetrachloride ($$\mathrm{$$CCl_4$$}) $$has a mass of $$39.75\ \mathrm{g}. $$What is its density?

Accepted Answer

$$1.59\ \mathrm{g/mL}$$

Introductory Chemistry Study Notes: Measurements, Metric System, Matter, Atomic Models, Periodic Table, Chemical Language, Reactions, Mole Concept, and Equation Calculations

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