Practice Test 49 - High School Chemistry

20 questions. Answer them in any order, then submit to see your score and every explanation.

A sodium ion is $\mathrm{Na^+}$ and the isotope is sodium-23 ( $^{23}$ Na). How many neutrons are in $\mathrm{^{23}Na^+}$ ?
A student reacts 15 g of metal M with 10 g of chlorine gas in a sealed container to form metal chloride: $\mathrm{M(s) + Cl_2(g) \rightarrow MCl_2(s)}$ . After the reaction, all the chlorine has reacted and no gas remains. What should be the mass of the solid product $\mathrm{MCl_2}$ ?
A school greenhouse uses fertilizer solutions that can be slightly acidic and contain dissolved salts. The irrigation tubing sits in sunlight and is filled and drained daily. The tubing must not chemically break down, clog from reactions, or contaminate the water delivered to plants. What chemical properties are needed for the tubing material?
Carbon dioxide forms by the reaction $\,CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O\,$ . If you start with 4.0 mol $CH_4$ and 6.0 mol $O_2$ , what is the maximum amount of $CO_2$ that can form?
A company needs a reusable bottle for transporting concentrated vinegar (acetic acid) for cleaning. Requirements: (1) must not react with the acid (safety is non-negotiable), (2) must survive being dropped occasionally, and (3) must stay under a moderate budget. Material options: - Glass: very chemically inert; low reactivity; but breaks easily when dropped. - HDPE plastic: good acid resistance; tough and drop-resistant; but can slowly absorb odors and may deform near high heat. - Aluminum: lightweight and tough; but can corrode in acids unless coated; coating can scratch. Which material is the best overall trade-off given the constraints?
A reusable water bottle company chose a BPA-free copolyester plastic instead of polycarbonate after customer concerns about chemical leaching. In an internal test, bottles were filled with water and held at $60^\circ$ C for 24 hours. The polycarbonate bottles showed measurable BPA in the water, while the copolyester bottles showed BPA below the detection limit. Which reasoning best justifies the material choice?
A single-step reaction diagram is shown. The reactants are at 60 kJ, the peak is at 130 kJ, and the products are at 100 kJ. Which statement is correct?
Fluorine (F), chlorine (Cl), and bromine (Br) are all in group 17 and commonly form −1 ions in ionic compounds. Which structural feature best explains this chemical similarity?
Carbon-14 (¹⁴C) is an isotope of carbon. How many protons and neutrons are in the nucleus of ¹⁴C?
In the nuclear equation $^{238}_{92}\text{U} \rightarrow {}^{234}_{90}\text{Th} + X,$ what particle is represented by $X$ ?
A student designs a container to store a concentrated bleach solution (sodium hypochlorite). Design 1 uses an aluminum bottle because it is lightweight and blocks light. After 10 days, the bottle shows pitting (small holes) on the inside, and the bleach concentration drops more than expected. The cap seal is still tight. Which refinement best addresses the chemical compatibility problem shown by the test results?
A student places a small piece of steel wool in a jar containing a small amount of water at the bottom (to keep the air humid). The jar is sealed and left for 3 days. The steel wool changes from shiny gray to reddish-brown and becomes more brittle. The mass of the steel wool changes from 2.00 g to 2.14 g. Did a chemical reaction occur? Choose the best CER justification.
A student measured the temperature change when different masses of ammonium nitrate (NH $_4$ NO $_3$ ) dissolved in 100.0 mL of water. The water started at 24.0°C in each trial. The salt was stirred until fully dissolved, then the final temperature was recorded. Data table: - Mass NH $_4$ NO $_3$ (g): 2.0, 4.0, 6.0, 8.0 - Final temperature (°C): 22.8, 21.5, 20.2, 19.0 Which statement best describes the trend?
Consider the balanced synthesis reaction: $\mathrm{N_2 + 3H_2 \rightarrow 2NH_3}$ What is the mole ratio of hydrogen gas ( $\mathrm{H_2}$ ) to ammonia ( $\mathrm{NH_3}$ )?
Which represents the correctly balanced equation (smallest whole-number coefficients)? AgNO3 + NaCl → AgCl + NaNO3
Arrange these period 2 elements in order of increasing atomic radius (smallest largest): fluorine (F) is group 17, carbon (C) is group 14, and lithium (Li) is group 1.
A student mixes cornstarch with water and notices it becomes thick and can act like a solid when pressed (a non-Newtonian mixture). The student wonders if a chemical change occurred, which matters for deciding how to dispose of it safely. Which investigation design best tests: Is mixing cornstarch and water a chemical change?
A student claims: "A chemical reaction occurred when solution X was mixed with solution Y." Evidence observed during mixing: 1) The mixture produced steady bubbles for about 20 seconds. 2) The temperature changed from 22.0°C to 22.2°C. 3) A solid formed and settled to the bottom after 1 minute. 4) The beaker used was made of glass. Which set of evidence best supports the claim?
Two processes are observed: Process 1: A reaction in a sealed bag causes the bag's temperature to rise from 22°C to 31°C. Process 2: A different reaction in a sealed bag causes the bag's temperature to fall from 22°C to 15°C. Which choice correctly classifies both processes and the energy flow direction?
A lab needs a spatula/scoop for transferring solid sodium hydroxide (NaOH) pellets. Requirements: must resist strong base (critical), must not contaminate samples, and should be durable. Budget is moderate. Materials: - Stainless steel: strong and durable; can be attacked by strong base over long exposure; moderate cost. - Nickel alloy: excellent resistance to strong base; durable; higher cost. - Aluminum: reacts with strong base; low cost; lightweight.

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