Hi,I am doing a practice test and need to check my answers. All of this is for Chem 101 Please see attached: **Question 1**Which of these are pure substances?I. Steam II. Crude oil III. Salt water IV. Gun powder V. Oxygen VI. Mercury - ○ I, II, and III- ○ I and III- ○ I, II, III, and V- ○ I, III, and V- ● I, V, and VI---**Question 2**A sample of heptane always contains 84% carbon and 16% hydrogen. Which of these best explains this phenomena?- ○ Law of Constant Composition- ○ Law of Conservation of Mass- ○ Dalton’s Atomic Theory- ○ Law of Mass Action- ○ Lavoisier’s Law---**Question 3**Which of these statements is not consistent with Dalton's atomic theory?- ○ All atoms of gold have the same chemical properties.- ● Electrons are equally distributed throughout an atom.- ○ The properties of sodium are different from the properties of chlorine.- ○ Compounds are formed when atoms combine in simple whole number ratios.- ○ Atoms are rearranged in normal chemical reactions but are neither created nor destroyed.

Since you have asked multiple questions, as per our guidelines,we are supposed to answer only one question and we will solve the first question for you.If you want any specific question to be solved then please specify the question number or post only that question. 1) If the substance is made up of only type of matter, It is called pure substance.The composition will be same throughout in pure substance. Also, in pure substance, chemical and physical properties are same. If the substance is made up of different type of matter, then it is called a mixture.In mixtures, the substances present in them are not chemically bonded and also, chemical and physical properties may vary. Given substances are steam, crude oil, saltwater, gunpowder, oxygen and mercury In the case of crude oil , it is a mix of different types of hydrocarbons.Also in gun powder, different components especially potassium nitrate, sulfur and charcoal are present in it. While in salt water, it contains mainly two different components. (i.e, salt and water). Hence in crude oil, gun powder and salt water composition is not same throughout and they can be grouped as mixtures. But in mercury and oxygen, only one type of substance is present (i.e, mercury and oxygen molecules respectively) Also,steam is water in vapor state and it contain only one kind of substance (i.e, H2O). So in steam, mercury and oxygen the composition is same throughout and it physical and chemical properties will remain also constant.Hence they are pure substance so the answer is "I , V and VI"